A man who was shot and killed by police in downtown Toronto early Saturday morning had been wanted for a double murder.

The slain man's uncle told CBC News that the man who was killed is named Kwasi Skene-Peters. Police had a warrant out for the 21-year-old's arrest in connection with the deaths of two men at a condo unit near Lisgar Street and Queen Street West in June.

Ontario's police watchdog, the Special Investigations Unit, is investigating Saturday's shooting. Earlier, it was unclear who shot the man, but the SIU confirmed to CBC News Saturday afternoon that it was police who shot him.

The SIU say the incident happened shortly after 2 a.m. ET when officers approached a vehicle on Peter Street. There was "an interaction" between officers and Skene-Peters, and the man was shot.

Emergency medical services were called at 3:05 a.m. with the report of a gunshot wound.

Toronto Paramedic Services transported Skene-Peters to St. Michael's Hospital, where he was pronounced dead at 3:59 a.m.

A man who had been smoking outside the nightclub Tryst, which is close to where the shooting happened, said he saw about 20 police officers driving towards the club at high speed. He said they parked by an alleyway near the club.

He said he didn't hear police make any demands before he heard 20 to 30 shots fired.

The man, who did not want CBC News to publish his name, said it sounded like a shootout.

"It was kinda scary, you know. I never really heard anything like that in my life so we just ran, that's the first thing we did. We ran across the street," he said.

He said he could see a man lying on the ground following the shooting.

When the shooting stopped, he filmed the aftermath. In the video, people can be heard repeatedly asking, "Why did you shoot?" It's not clear in the video who is asking the question, or who they are directing their question to.

Nelson Haines, the manager at Tryst, said they've never had anything like this happen at their club before.

"When we heard the shooting, we let people run into our building," he said. "We then barricaded our doors and kept people safe."

Haines said no one tried to get in with a gun that evening.

The SIU has assigned five investigators and four forensic investigators to the case. The unit is called in when police officers in Ontario are involved in incidents where someone has been seriously injured or died.

The SIU is asking anyone with information about what happened to call the lead investigator at 1-800-787-8529 ext. 1886.