BOSTON (CBS) – The brother of a man who was shot and killed by police in Boston Tuesday was very vocal on social media. Usaamah Rahim’s older brother is an imam at a mosque in California.

Ibrahim Rahim posted his account of what happened on Facebook:

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“My youngest brother Usaama Rahim was waiting for the bus to go to his job. He was confronted by three Boston Police officers and subsequently shot in the back three times. He was on his cell phone with my dear father during the confrontation needing a witness. His last words to my father who heard the shots were: I can’t breathe!”

A federal law enforcement source says Usaamah Rahim, 26, of Roslindale, had been on investigators’ radar for several months and recently became radicalized and inspired by ISIS’ online propaganda.

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Police say he was armed with a knife and was approaching the officers.

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A man was shot and killed by the Joint Terrorism Task Force in Boston (WBZ-TV)

A man was shot and killed by the Joint Terrorism Task Force in Boston (WBZ-TV)

The imam’s followers in Oakland say they’re concerned about the way 26-year-old Usaamah Rahim was being followed by law enforcement and argue that his brother is adamantly opposed to extremism.

“Imam Ibrahim preaches a brand of Islam that stresses compassion and love for one another,” a follower said Tuesday. “What I do know is that Imam Ibrahim is in no way, shape or form connected with any extreme, fringe elements that would espouse any type of terrorist-like activity.”

During a press conference Tuesday, authorities would not say if Rahim was on the phone during the fatal confrontation. But they did say they have video evidence proving their account of what happened and are planning to share it with the Islamic Society of Boston.

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KPIX reports that Imam Ibrahim was traveling to Boston Tuesday night.