Soldiers, police and firefighters stood solemnly together with relatives of the victims during the Islamic prayer service.

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Al Qadri suddenly excuses himself as he and his supporters move to an adjoining room, where he leads them in regular Islamic prayer, or salah.

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Saudi's religious police enforce the kingdom's strict Islamic laws, including dress and prayer times.

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The real missed opportunity to intervene before the bombs went off in Boston likely came three months earlier, when bombing suspect Tamerlan Tsarnaev stood up during a Friday prayer service at his mosque - the Islamic Society of Boston, in Cambridge - to angrily protest the imam's sermon.

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These shrines have long been a focus of devotion and prayer, but hardline Islamists have decided that worship at them is un-Islamic.

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An elder at the Islamic Society of Boston Cultural Center, the largest mosque in New England, said Tamerlan occasionally attended Friday prayer services at the mosque in the past year and a half.

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