A man died following a "medical emergency" while being detained by police in Northern California on Monday, authorities said.
Officers in Alameda, a small island community in the shadows of Oakland across the bay from San Francisco, responded to the 800 block of Oak Street around 10:45 a.m. Monday after they got "two separate reports of a male who appeared to be under the influence and a suspect in a possible theft," police said in a statement.
"Officers attempted to detain the man and a physical altercation ensued," the statement continued. "At that time, the man had a medical emergency."
The suspect was taken to a nearby hospital, where he died.
Conor Acomb, 42, of Oakland, had just left a bank when he "saw the commotion" and slowed down to look.
"I saw a gentleman writhing on the ground with two officers over him," Acomb said in an interview. "It looked like he was having a heart attack."
Officers performed CPR for at least 15 minutes before the man was taken away by an ambulance, Acomb said.
The incident drew a massive police response.
"I looked down Oak Street and saw about 12 patrol cars and dozens of cops," Acomb said. "It was an overwhelming police presence."
The Alameda County Sheriff's Department and the district attorney's office are conducting separate investigations, police said.
The man's name, age and race were not immediately disclosed.