At 73 years old, Francisco Serna was in the early stages of dementia, going on late-night walks in his Bakersfield, California neighborhood when he found himself unable to sleep.

On Monday, just after midnight, he was killed by police during one of these walks.

Bakersfield police say they were responding to a report of a man with a gun when a neighbor pointed in Serna’s direction, prompting police to shoot him nine times, killing him on the spot.

But Serna was unarmed, doing nothing but standing in a neighbor’s driveway. Enough to apparently strike fear in the hearts of the responding officers, although police have not disclosed exactly what he was doing to merit being killed.

“My dad did not own a gun,” his son, Roy Serna, told the Los Angeles Times.

“He was a 73-year-old retired grandpa, just living life. He should have been surrounded by family at old age, not surrounded by bullets.”

Even though police found no gun on Serna after they killed him, they still searched his family’s home and car to guns, apparently in an effort to find some kind of justification for killing him.

The father of five spent years working at a cotton gin before retiring just over ten years ago. He lived with his wife and one of his daughters. His son, Rogelio, lived a few blocks away.

He began showing signs of dementia in 2015 and also experienced the occasional delusion, but the illness progressed in the past month.

Roy Serna told the Los Angeles Times that Bakersfield police had responded to his father’s home on two prior occasions when the elderly man became confused and activated a medical alarm.

The younger Serna posted a video to Facebook, asking people to join them at a candlelight vigil for his theater Tuesday night on the street he was killed.

“We want the TRUTH to be told,” he wrote on Facebook. “My father was MURDERED by BAKERSFIELD POLICE DEPARTMENT.”