PORTLAND, Ore. – A Portland police officer fired after fatally shooting a driver – only to be later reinstated – returned to work this week and opened up about the shooting that he said never leaves his mind.

"There isn't a night that's gone by that I haven't thought about it," said Lt. Jeffrey Kaer, who killed Dennis Young (pictured below) in January of 2006.

The incident started when Kaer's sister called him because she noticed a suspicious car parked in front of her house. Her son had recently been shot in a road rage incident.

Kaer went to the scene without informing police dispatchers of his actions.

When Kaer arrived and approached the vehicle, he found a man asleep behind the wheel and called for backup.

After tapping on the driver's side window and getting no response, Kaer opened the door and shook the driver to try to wake him up.

"All's he had to do was undo his seatbelt, and he would have went to jail," Kaer said.

The suspect reportedly became combative and gunned the accelerator. The car drove into a tree, and police said Young then placed the car in reverse and drove backward toward Kaer and another officer. Kaer fired two shots.

"Well, I was trying to get out of the way, but in that 1.6 seconds, that's all I had to recognize what was happening, formulate a plan and take action," Kaer said. "I wasn't even aiming when I fired my two rounds."

An autopsy found Young died of a single wound to the upper torso. The second bullet hit the car.

Investigators later learned that Young was on parole, wanted, in a stolen car while high on methamphetamine and had a large hunting knife in the front seat.

A grand jury and police review board cleared Kaer, but Mayor Tom Potter fired him after determining the officer had made "questionable choices."

"It felt more like a vendetta," Kaer said of Potter's decision. "I don't want to put ideas or words in his mouth, but it appeared that he was trying to use me as some kind of political, you know, chip in the pot."

An arbitration judge last month said Potter was wrong to fire Kaer, and the officer was reinstated.

Kaer said he never should have been fired but said he has no hard feelings for anyone outside of City Hall.

"I'm not denying my own responsibility in any way, shape or form," he said. "Am I sorry it happened? Absolutely."