Dozens of supporters have gathered outside the motel where Martin Luther King Jr. was slain to pray for a young man who was fatally shot in the back of an Arkansas patrol car.

The vigil Monday night outside the National Civil Rights Museum in Memphis, Tenn., came hours after police released an autopsy report in the death of 21-year-old Chavis Carter.

The report said Carter's death was a suicide, but several people at the vigil continued to question how a man in handcuffs could shoot himself in the head.

Police said officers in Jonesboro, Ark., searched Carter twice but didn't find a gun before he was fatally shot July 28.

Carter's mom, Teresa Carter, wiped her eyes as people spoke about her son.

"My heart is so heavy," she said.