TENNESSEE, USA (AP) — A man police say shot himself in the head while his hands were cuffed behind him in the back of an Arkansas patrol car tested positive for methamphetamine, anti-anxiety medication and other drugs, according to an autopsy report released Monday that listed his death as a suicide.

The state crime lab report said the muzzle of a handgun that Chavis Carter apparently concealed from arresting officers was placed against his right temple when it was fired. The report, signed by three medical examiners, included a drug analysis showing Carter's urine and blood indicated methamphetamine and other drug use.

The report, released to The Associated Press and other news organisations under a Freedom of Information Act request, said Carter's blood also tested positive for at least trace amounts of the anti-anxiety medication diazepam and the painkiller oxycodone. His urine test also returned a positive result for marijuana.

The report said Carter's death was ruled a suicide based on autopsy findings and investigative conclusions from the Jonesboro Police Department, which has faced questions from Carter's family and community members about the circumstances surrounding the July 28 shooting.

"He was cuffed and placed into a police car, where apparently he produced a weapon, and despite being handcuffed, shot himself in the head," the report said.

Benjamin Irwin, a Memphis, Tennessee lawyer representing Carter's family, declined to comment on the specifics of the toxicology report, calling instead for police to release details of any gunpowder residue or other such tests.

"If those tests were taken ... what were the results?" Irwin asked.

On Monday night dozens of Carter family supporters gathered outside the National Civil Rights Museum in Memphis for a candlelight vigil.

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

"My heart is so heavy," she said.

She didn't talk about the autopsy results as she addressed the small crowd, but others did. One man read part of the autopsy report as he stood at the podium and some continued to demand answers about how Chavis Carter died.

Police have said officers frisked Carter, 21, twice after a traffic stop without finding a gun before he was fatally shot, but the department's internal investigation continues. The FBI also is monitoring the case, and the local branch of the NAACP has called for a thorough investigation into the death of Carter, who was black. Two other men who were in a truck with him during the stop and the two officers who were on the scene are white, according to police.