Photos: Interfaith service for the victims of the Boston Marathon bombings

US President Barack Obama and First Lady Michelle Obama (C) attend the "Healing Our City: An Interfaith Service" dedicated to those who were gravely wounded or killed in the Boston Marathon bombing, at the Cathedral of the Holy Cross in Boston, Massachusetts, on April 18, 2013. Obama mourns victims of the deadly marathon attacks, as investigators study images of a suspect who may have planted the bombs. No arrests have been made in connection with Monday's twin bombings near the finish line of the race, which sent metal fragments and nails into a crowd of thousands of runners and spectators, killing three people and wounding 180. Seated next to Mrs. Obama is Massachussetts Governor Deval L. Patrick. AFP PHOTO/Jewel SAMAD/AFP/Getty Images ( 519016889 )

President Barack Obama attends the "Healing Our City: An Interfaith Service" at the Cathedral of the Holy Cross in Boston, Thursday, April 18, 2013. The service is dedicated to those who were gravely wounded or killed in Mondayís bombing near the finish line of the Boston Marathon. (AP Photo/Susan Walsh) ( Obama Boston Marathon Explosions )

People queue for security check outside the Cathedral of the Holy Cross where U.S. President Barack Obama is scheduled to attend an interfaith service for the victims of the Boston Marathon bombings in Boston, Massachusetts April 18, 2013. Obama was due to visit Boston on Thursday to attend a memorial service for victims of the Boston Marathon bombing amid a manhunt for a suspect seen on video taken before two blasts struck near the finish line on Monday. REUTERS/Jessica Rinaldi ( USA-EXPLOSIONS/BOSTON )

President Barack Obama, first lady Michelle Obama and Massachusetts Gov. Deval Patick attend an interfaith healing service at the Cathedral of the Holy Cross in Boston, Thursday, April 18, 2013, for victims of Monday's Boston Marathon explosions. (AP Photo/Susan Walsh) ( Obama Boston Marathon Explosions )

People gather outside of the Cathedral of the Holy Cross as US President Barrack Obama and wife Michelle attend an interfaith prayer service to honor the victims of the Boston Marathon bombings April 18, 2013 in the South End neighborhood of Boston, Massachusetts. AFP PHOTO/Stan HONDA/AFP/Getty Images ( 519016577 )

U.S. President Barack Obama arrives for an interfaith memorial service at the Cathedral of the Holy Cross for the victims of the Boston Marathon bombing in Boston, Massachusetts April 18, 2013. REUTERS/Kevin Lamarque ( USA-EXPLOSIONS/BOSTON-OBAMA )

US President Barack Obama attends the "Healing Our City: An Interfaith Service" dedicated to those who were gravely wounded or killed in the Boston Marathon bombing, at the Cathedral of the Holy Cross in Boston, Massachusetts, on April 18, 2013. AFP PHOTO/Jewel SAMAD/AFP/Getty Images ( 519016828 )

U.S. President Barack Obama (L) and first lady Michelle Obama (2nd L) attend an interfaith memorial service at the Cathedral of the Holy Cross for the victims of the Boston Marathon bombing in Boston, Massachusetts April 18, 2013. Massachusetts Governor Deval Patrick sits with the Obamas. REUTERS/Kevin Lamarque ( ( USA-EXPLOSIONS/BOSTON-OBAMA )

U.S. President Barack Obama and his wife Michelle attend an inter-faith memorial service for the victims of the bombing at the Boston Marathon in Boston, Massachusetts April 18, 2013. REUTERS/Brian Snyder ( USA-EXPLOSIONS/BOSTON )

A nun holds a pair of rosary beads along with her ticket as she waits to enter the Cathedral of the Holy Cross where U.S. President Barack Obama is scheduled to attend an interfaith service for the victims of the Boston Marathon bombings in Boston, Massachusetts April 18, 2013. REUTERS/Jessica Rinaldi ( USA-EXPLOSIONS/BOSTON )

President Barack Obama and first lady Michelle Obama arrive for an interfaith healing service at the Cathedral of the Holy Cross in Boston, Thursday, April 18, 2013, for victims of Monday's Boston Marathon explosions. (AP Photo/Charles Krupa) ( Obama Boston Marathon Explosions )

President Barack Obama attends an interfaith healing service at the Cathedral of the Holy Cross in Boston, Thursday, April 18, 2013, for victims of Monday's Boston Marathon explosions. (AP Photo/Charles Krupa) ( Obama Boston Marathon Explosions )

U.S. President Barack Obama and his wife Michelle attend an inter-faith memorial service for the victims of the bombing at the Boston Marathon in Boston, Massachusetts April 18, 2013. REUTERS/Brian Snyder ( USA-EXPLOSIONS/BOSTON )

A young boy holds a Boston Marathon Medal with black tape, signifying mourning, as he and his father stand near the Cathedral of the Holy Cross as US President Barrack Obama and wife Michelle attend an interfaith prayer service to honor the victims of the Boston Marathon bombings April 18, 2013 in the South End neighborhood of Boston, Massachusetts. AFP PHOTO/Stan HONDA/AFP/Getty Images ( 519016345 )

U.S. President Barack Obama greets Rep. Ed Markey (D-MA) (L) as U.S. first lady Michelle Obama greets Massachusetts Governor Deval Patrick as they arrive at Logan Airport in Boston to attend an interfaith memorial service at the Cathedral of the Holy Cross for the victims of the Boston Marathon bombing April 18, 2013. REUTERS/Kevin Lamarque ( USA-EXPLOSIONS/BOSTON-OBAMA )

President Barack Obama and first lady Michelle Obama walk up the stairs of Air Force One at Andrews Air Force Base, Md. Thursday, April 18, 2013. ( AP Photo/Jose Luis Magana) ( Obama )

President Barack Obama walks in the rain prior to boarding Air Force One at Andrews Air Force Base in Md., Thursday, April 18, 2013. Obama is traveling to Boston to attend the "Healing Our City: An Interfaith Service" dedicated to those who were gravely wounded or killed in Mondayís bombing near the finish line of the Boston Marathon. (AP Photo/Susan Walsh) ( Obama )

U.S. President Barack Obama and first lady Michelle Obama walk towards Marine One before they depart the White House in Washington, on their way to a memorial service in Boston for victims of the bomb explosions at the finish line of the Boston Marathon on Monday, April 18, 2013. REUTERS/Larry Downing ( OBAMA/ )

Former Massachusetts Governor and 2012 Republican presidential nominee Mitt Romney attends an interfaith prayer service for victims of the Boston Marathon attack titled "Healing Our City," where President Barack Obama spoke at the Cathedral of the Holy Cross on April 18, 2013 in Boston, Massachusetts. (Photo by Spencer Platt/Getty Images) ( 166906339 )

Boston Mayor Thomas Menino speaks at an interfaith prayer service for victims of the Boston Marathon attack titled "Healing Our City," at the Cathedral of the Holy Cross on April 18, 2013 in Boston, Massachusetts. (Photo by Spencer Platt/Getty Images) ( 166906729 )

President Barack Obama speaks at an interfaith prayer service for victims of the Boston Marathon attack titled "Healing Our City," at the Cathedral of the Holy Cross on April 18, 2013 in Boston, Massachusetts. (Photo by Spencer Platt/Getty Images) ( 166906730 )

Boston Mayor Thomas Menino pauses after speaking at an interfaith prayer service for victims of the Boston Marathon attack titled "Healing Our City," at the Cathedral of the Holy Cross on April 18, 2013 in Boston, Massachusetts. Authorities investigating the attack on the Boston Marathon have shifted their focus to locating the person who placed a black bag down and walked away just before the bombs went off. The twin bombings at the 116-year-old Boston race, which occurred near the marathon finish line, resulted in the deaths of three people and more than 170 others injured. (Photo by Spencer Platt/Getty Images) ( 166906733 )

President Barack Obama speaks at an interfaith prayer service for victims of the Boston Marathon attack titled "Healing Our City," at the Cathedral of the Holy Cross on April 18, 2013 in Boston, Massachusetts. (Photo by Spencer Platt/Getty Images) ( 166907870 )

President Barack Obama speaks at an interfaith prayer service for victims of the Boston Marathon attack titled "Healing Our City," at the Cathedral of the Holy Cross on April 18, 2013 in Boston, Massachusetts. (Photo by Spencer Platt/Getty Images) ( 166908012 )

President Barack Obama speaks at an interfaith prayer service for victims of the Boston Marathon attack titled "Healing Our City," at the Cathedral of the Holy Cross on April 18, 2013 in Boston, Massachusetts. (Photo by Spencer Platt/Getty Images) ( 166908013 )

U.S. President Barack Obama talks to Cardinal Sean O'Malley during an interfaith memorial service for the victims of the bombing at the Boston Marathon in Boston, Massachusetts April 18, 2013. REUTERS/Brian Snyder ( USA-EXPLOSIONS/BOSTON )

People attend the interfaith memorial service at the Cathedral of the Holy Cross for the victims of the Boston Marathon bombing in Boston, Massachusetts April 18, 2013. Obama told a memorial service for the Boston bombing victims that "we will find" whoever carried out the attack that killed three people as investigators search for two men seen on a video of the scene shortly before the blasts. REUTERS/Kevin Lamarque ( USA-EXPLOSIONS/BOSTON )

People rise to applaude as U.S. President Barack Obama speaks at an interfaith memorial service at the Cathedral of the Holy Cross for the victims of the Boston Marathon bombing in Boston, Massachusetts April 18, 2013. REUTERS/Kevin Lamarque ( USA-EXPLOSIONS/BOSTON )

President Barack Obama pauses while speaking at the "Healing Our City: An Interfaith Service" at the Cathedral of the Holy Cross in Boston, Thursday, April 18, 2013. (AP Photo/Susan Walsh) ( Obama Boston Marathon Explosions )

US President Barack Obama speaks during "Healing Our City: An Interfaith Service" dedicated to those who were gravely wounded or killed in the Boston Marathon bombing, at the Cathedral of the Holy Cross in Boston, Massachusetts, on April 18, 2013. AFP PHOTO/Jewel SAMAD/AFP/Getty Images ( 519018889 )

US President Barack Obama speaks during "Healing Our City: An Interfaith Service" dedicated to those who were gravely wounded or killed in the Boston Marathon bombing, at the Cathedral of the Holy Cross in Boston, Massachusetts, on April 18, 2013. AFP PHOTO/Jewel SAMAD/AFP/Getty Images ( 519018895 )

Musician Yo-Yo Ma performs during "Healing Our City: An Interfaith Service" dedicated to those who were gravely wounded or killed in the Boston Marathon bombing, at the Cathedral of the Holy Cross in Boston, Massachusetts, on April 18, 2013. AFP PHOTO/Jewel SAMAD/AFP/Getty Images ( 519019318 )

US President Barack Obama speaks during the "Healing Our City: An Interfaith Service" dedicated to those who were gravely wounded or killed in the Boston Marathon bombing, at the Cathedral of the Holy Cross in Boston, Massachusetts, on April 18, 2013. AFP PHOTO/Jewel SAMAD/AFP/Getty Images ( 519019699 )

President Barack Obama, accompanied by Massachusetts Gov. Deval Patrick, center, and Boston Mayor Thomas Menino, speaks to Boston Athletic Association volunteers after attending the "Healing Our City: An Interfaith Service" at the Cathedral of the Holy Cross in Boston, Thursday, April 18, 2013. Menino wear a protective boot after breaking a toe. (AP Photo/Susan Walsh) ( Obama Boston Marathon Explosions )

President Barack Obama, first lady Michelle Obama and Massachusetts Gov. Deval Patrick attend the "Healing Our City: An Interfaith Service" at the Cathedral of the Holy Cross in Boston, Thursday, April 18, 2013. (AP Photo/Susan Walsh) ( Obama Boston Marathon Explosions )

President Barack Obama speaks during an interfaith healing service at the Cathedral of the Holy Cross in Boston, Thursday, April 18, 2013, for victims of Monday's Boston Marathon explosions. (AP Photo/Charles Krupa) ( APTOPIX Obama Boston Marathon Explosions )