"We said to the FBI, listen if you want someone to negotiate with the younger brother..." Yusufi Vali, the spokesperson for the Islamic Society of Boston in Cambridge, Mass., told ABC News. "We said we are willing to send in someone because he may have been a Muslim -- to talk to him and negotiate that process and the FBI was so grateful for that."
The standoff ended before leaders of the mosque could intervene. But during a week bookended by terror plots, the effort was one of several instances where members of the Muslim community sought to assist authorities as they confronted plots by radicals.
In Canada Monday, authorities said they were tipped off by members of the Muslim community about a plot by two men with ties to al Qaeda to derail passenger trains. In Cambridge, it was the leadership of the mosque that initially tried to confront Tamerlan Tsarnaev about his extremist views, . And later, they tried to help the FBI end its standoff with the younger Dzhokhar without more bloodshed.
The FBI didn't immediately get back to them and they didn't end up being in the negotiations that led to his capture, but Vali said the FBI did thank them for the offer.
The brothers were not formal members of the Cambridge mosque, but Tamerlan did attend prayers intermittently on Fridays as well as occasionally attending daily prayers, according to the mosque. Dzhokhar attended less frequently, but would occasionally visit to pray. Tamerlan's wife, a convert to Islam Katherine Russell, did not attend the mosque and was not known to any members, Vali said.
In recent months, Tamerlan Tsarnaev's growing radicalism led him to disrupt services, and prompted leaders of the mosque to intervene.
On November 16, 2012 a preacher at the Islamic Society of Boston gave a sermon telling the congregants it was just as appropriate to celebrate Thanksgiving, which was coming up, and July 4th as the Prophet Mohammed's birthday. Tsarnaev interrupted the service with an outburst saying the celebration of national holidays was not allowed in the Muslim faith.
On January 18th, 2013 one of the preachers said, "Martin Luther King is a great man, he is always going to be remembered as a great man," also while discussing the Prophet Mohammed. The elder Tsarnaev brother again stood up and challenged the preacher, but this time actually calling the preacher a "non-believer" and a "hypocrite."
"At which point the congregation and the people of the congregation started shouting at him, 'You need to leave!,' Vali said, recounting the incidents. "Which just kind of shows you how--both of these incidents show how the mosque really teaches an American Islam and how people inside the congregation believe in that and want to protect that."
Vali says Tsarnaev left, but afterwards the leaders of the mosque sat down with him and told him he had a "clear choice."
"Either you are silent from now on during the sermons...or you're not going to be welcome here," Vali recounted, noting there were no other outbursts or disruptions.
"The important thing to remember is the ethos of that congregation is to serve American society," Vali said. "We've got several lawyers, teachers, doctors, public servants, even law enforcement inside that institution who really believe in an American Islam and I think that's what those guys were reacting to."
Vali says the incidents prove Tsarnaev could not have been radicalized at their mosque.
"Here's what we do know about the radicalization, based on the two incidences it did not happen in the mosque," Vali said. "These guys were reacting to the fact that Martin Luther King was being celebrated and that we want to celebrate July 4th and Thanksgiving so that I think is clear."
Vali says the Muslim community is "hurt" and "shocked" by the "disgraceful, terrible acts" and they immediately contacted the FBI when they learned the suspects had attended the mosque. They urged members who knew the brothers to do the same.
"The Islam we project is moderate and it's an American Islam which is the way I understand it and it really respects the cultural and legal contours of America," Vali said, adding that the Muslim community in Boston is against this "extreme version of Islam as anyone in American -- because we are Americans."
"I share this commitment to root this evil out," Vali said, noting that when he learned of the suspects' faith he thought "if these guys were Muslim who did this and in the name of Islam I could not recognize them as part of my city or as part of my faith community, that's how I felt."
"They are not mine because it's absolutely disgraceful what they did," Vali said.
Vali is not worried about a backlash against Muslims in Boston because Boston is a "community that really pulls together," noting they almost immediately began receiving e mails of support after the bombings took place at the Boston marathon on April 15th. Three people were killed and over 200 were injured.