A Ramsey County grand jury has concluded police officers were justified using deadly force in the September shooting of a St. Paul man family members described as psychotic.

The officer who shot Philip Quinn will not face criminal charges, Ramsey County Attorney John Choi told reporters on Thursday afternoon, a day after the grand jury reached its conclusions.

St. Paul police chief Thomas Smith and Ramsey County attorney John Choi announce Thursday that a grand jury returned no indictment in the Philip Quinn officer-involved shooting that took place in September 2015. Riham Feshir | MPR News

In an unusual move, Choi and Police Chief Tom Smith provided reporters with transcripts and video and laid out a timeline detailing how the police call unfolded. Choi said he released details of the incident in an effort to be as transparent as possible, and shared them with Quinn's family ahead of the news conference.

"This was a tragic event" for Quinn's family and for the officers involved, Smith said. Officers did exactly what they were supposed to do, he added.

"There are times when we have to defend ourselves and others. Officer (Rich) McGuire was put in a terrible situation. He did everything he was trained to do, and still had no other choice in this situation," he said.

Police said they were called to a home around 6 p.m. Sept. 24 on a report of a suicidal man, later identified as Quinn, 30. Quinn's relatives said they'd called 911 that evening hoping authorities would come to the man's aid in his time of crisis.

Protesters march down University Avenue, demanding charges against St. Paul police who shot and killed 30-year-old Philip Quinn in September, 2015. Tim Nelson | MPR News 2015

Family members couldn't be reached for comment Thursday but told the St. Paul Pioneer Press in December that officers should have taken a different tack because they knew Quinn was mentally ill.

In January, St. Paul police officials said the department would no longer investigate cases in which its own police are involved in deaths or serious injury and would instead refer the cases to the Minnesota Bureau of Criminal Apprehension or the Hennepin County Sheriff's Office. That decision was made in the wake of the police shooting of Quinn and the January 2015 shooting of Marcus Golden.

On Thursday, Smith said police had received several calls that day from Quinn's family about his behavior. He said Quinn's girlfriend had called 911 saying Quinn was acting "bizarre, psychotic," Smith related. Quinn had a screwdriver and his mother had said he stabbed himself numerous times and believed that he had died and come back to life, Smith added.

Officers, he added, did not confront Quinn but said they were there to help him. "Quinn initiated contact with officers. Our officers weren't trying to arrest him. They took positions of cover while Quinn was in the garage pacing back and forth. They didn't call him out. They didn't say, 'You're under arrest.'"

Smith said the confrontation escalated when Quinn ran out of the garage directly at an officer in a "very aggressive manner." The officer retreated shouting numerous times to drop the screwdriver until the officer was backed up against a fence and forced to fire, he said.

In the dashcam video released Thursday an officer can be heard shouting at Quinn to drop an object in his hand. Police say Quinn charged at the officer. Police fired four shots in all. Two bullets struck Quinn.

Frame grab of squad car dash camera video released by police of the shooting of Philip Quinn in Sept. 2015. St. Paul Police Department

The Ramsey County Medical Examiner said one went through Quinn's forearm. The other struck a vein near his hip, causing him to bleed to death. Toxicology tests revealed Quinn had been using amphetamine and methamphetamine.

Asked why officers didn't first try to stun Quinn with a Taser, Smith said the situation unraveled quickly while officers were waiting for a K-9 to arrive. Given "how fast this happened, from zero to 100 in the blink of an eye, there was no opportunity for the officer to use a Taser."

Smith noted there was one thing he and the Quinn family agreed on: the man needed help with his mental illness.

"If Philip Quinn would have had opportunity to have an open bed and to get some help, this tragedy probably would not have occurred," he said.