OAKLAND — A man shot and killed by terrorism investigators Tuesday in Boston is the younger brother of an imam at a North Oakland mosque who is questioning authorities’ account of what led to the shooting. Authorities with the Joint Terrorism Task Force said they approached 26-year-old Usaama Rahim in Boston about 7 a.m. to question him about “some terrorist-related information.” Rahim, who was under 24-hour surveillance, allegedly lunged at officers with a large military-style knife.

He was shot after police asked him to drop the knife, Boston Police Commissioner Williams Evans.

Ibrahim Rahim, the man’s older brother, said his brother was at a bus stop on his way to work when the officers confronted him and shot him three times in the back.

“He was on his cell phone with my dear father during the confrontation needing a witness,” Ibrahim Rahim wrote on Facebook. “His last words to my father who heard the shots were, ‘I can’t breathe.’

“We are deeply grieved by the loss of my younger brother,” he said.

The elder Rahim, imam of Lighthouse Mosque, was traveling to Boston to be with family, his assistant imam Sundiata Rashid said outside the Oakland mosque Tuesday afternoon.

Ibrahim Rahim came to Oakland from Boston six months ago to lead the mosque on Martin Luther King Jr. Boulevard and was immediately a “positive force” for Oakland and its Muslim community, Rashid said.

Abdi Samatar, who came to the mosque for a daily prayer, described the imam as a peaceful preacher.

“(They) are grieving because of the loss and we feel it’s a tragedy,” Rashid said. “This is one of the things that can happen … another black man killed by law enforcement and a Muslim killed by law enforcement.” Ibrahim Rahim could be not be reached for comment.

Before the shooting, Evans said officers repeatedly ordered Rahim to drop the knife, but he continued to move toward them with it. He said task force members fired their guns, hitting Rahim once in the torso and once in the abdomen. He was taken to a hospital, where he was pronounced dead.

Neither Evans nor Vincent Lisi, the special agent in charge of the Boston FBI office, would say why Rahim was under surveillance, but Evans said a “level of alarm” prompted authorities to try to question him Tuesday.

“Obviously, there was enough information there where we thought it was appropriate to question him about his doings,” Evans said. “He was someone we were watching for quite a time.”

Evans said the officers didn’t have their guns drawn when they approached Rahim. He said police have video showing Rahim “coming at officers” while they are backing away.

Ibrahim Hooper, a spokesman for the Council of American-Islamic Relations, said the group will monitor the investigation.

“We have a number of questions: Why exactly was he being followed? What was the probable cause for this particular stop? Were there any video cameras or body cameras of the incident? How do you reconcile the two versions of the story, the family version being that he was on his normal commute to work at a bus stop?” Hooper said.

Boston voter registration records for Usaama Rahim list him as a student. Records indicate that as recently as two years ago he was licensed as a security officer in Miami but do not specify in what capacity.

On Tuesday afternoon, authorities raided a home in Everett in connection with the case.

“It’s all part of a very active Joint Terrorism Task Force investigation,” Boston police spokesman Lt. Michael McCarthy said.

The officer and the agent involved in the shooting were evaluated at a hospital for what Evans described as “stress,” though they weren’t physically injured.

Lisi said authorities “don’t think there’s any concern for public safety out there right now.”

The Associated Press contributed to this report.