Edwin Michael Adams, 56, died after a police pursuit along San Francisco’s Mission Street. Three witnesses said a man who appeared to be a plainclothes officer tackled Adams off his motorized scooter and into a bus shelter, where his head struck a metal pole.

San Francisco police said Adams collided with a street fixture after the pursuit and was pronounced dead at a hospital. The department said officers pursued him because he had a warrant, but did not describe a tackle.

Adams’ public defenders said the warrant stemmed from an alleged failure to charge his ankle monitor. Sheriff’s spokesperson Tara Moriarty said deputies requested a warrant after Adams violated the terms of his monitoring arrangement. San Francisco Superior Court records show the warrant was issued Oct. 10, less than a week before the pursuit. The district attorney’s office is investigating his death, a spokesperson said.