Video shows officer breaking down after shooting unarmed man

Newly-released video shows a devastated US police officer breaking down moments after shooting dead an unarmed suspect.

Montana police officer Grant Morrison killed Richard Ramirez in April last year.

The 38-year-old suspect was high on methamphetamine in the back seat of a car when he six times refused Morrison's demand to raise his hands.

Morrison told the inquest into Ramirez's death that he thought the suspect was reaching for gun.

"I couldn't take that risk ... I wanted to see my son grow up," he said.

In a dashcam video shown to the inquest the officer appears to collapse after realising the man he shot three times was unarmed.

He can be heard saying "I thought he was going to pull a gun" before he places his head in his hands as other officers comfort him.

Ramirez, who had two outstanding warrants on him on when he died, was suspected of taking part in an armed robbery earlier that night that resulted in a 61-year-old man being shot.

Last week a coroner ruled Ramirez's death was a non-criminal, justifiable homicide.

Morrison was also cleared of any wrongdoing in a 2013 shooting.