The San Francisco Police Department said officers spotted Adams riding a scooter at about 11:24 a.m. and tried to arrest him because of an outstanding warrant. According to the department, he fled and collided with a street fixture. Officers provided medical aid before paramedics took him to a hospital, where he was pronounced dead.

Three witnesses gave a different account, saying a plainclothes person who appeared to be an undercover officer tackled Adams into the shelter. They said a gray sedan sped up, crossed into oncoming traffic and tried to cut him off as he rode against traffic. One witness described the takedown as a “football tackle.”

The department did not respond to questions about the witnesses’ account or what the warrant was for. It has not publicly explained what led officers to pursue Adams. The circumstances of his death remain unclear.

The San Francisco Public Defender’s Office said it had represented Adams on nonviolent charges that he had not yet had a chance to contest at trial. A spokesperson called for a thorough, independent investigation into why police pursued him and what led to his death.

Jail booking logs and Superior Court records show Adams was arrested at least four times between March 12 and Sept. 2 on nonviolent charges, including allegations involving possession of methamphetamine and cocaine with intent to sell, and contempt of court. Records show he was released in early September with an ankle monitor as a condition of appearing in court. It is not known whether he was wearing the monitor during the pursuit.

San Francisco police policy on foot pursuits, which also governs pursuits of people on scooters, directs officers to weigh the need for an immediate arrest against risks to the person being pursued, officers and the public.