On April 14 last year, Morrison, from Billings in Montana, had stopped a car in which Richard Ramirez, 38, was a passenger.

Morrison repeatedly ordered Ramirez and the other four occupants to get out of their car, police footage shows.

The officer testified before a coroner's inquest this month that he saw Ramirez "reach for his waistband" during the 30-second encounter and he feared for his life.

"I thought he was going to pull a gun on me," Morrison is heard saying through tears on the video..

He shot Ramirez, who was high on methamphetamine.

Police officers did not find any guns in the car, just a syringe.

A jury at the inquest ruled last Wednesday that the shooting was a non-criminal, justifiable homicide.

"I knew in that moment, which later was determined to be untrue, but I knew in that moment that he was reaching for a gun," Morrison told the inquest.

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

In the video of the shooting, the back seat of the car largely obscures Ramirez's actions, although Morrison can be seen withdrawing his weapon and shooting into the vehicle at close range.

An autopsy reveals the fatal shot hit Ramirez in the chest and punctured his lung, while a toxicology report indicates he had a dose of methamphetamine in his system when he died.

Ramirez family members said they were disappointed by the ruling and intended to file a lawsuit against Morrison and the Billings Police Department, alleging excessive use of force, his sister Julie Ramirez said.

In 2013, Morrison shot and killed another man, Jason Shaw, 32.

Morrison was cleared of any wrongdoing in that incident as well.

The verdict clearing Morrison of any charges comes as police killings of unarmed suspects in Ferguson, Missouri and New York City draw international attention and increased scrutiny of the police.

Of the 15 people called to testify during the two-day Billings inquest, 12 were from law enforcement.

- with AP