(CBSNews) BAKERSFIELD, Calif. -- An unarmed 73-year-old with dementia who was shot and killed by police early Monday was struck nine times, the man’s son said in a video posted to Facebook. However, police say the son is “misinformed.”

The officer was answering a report of a man brandishing a handgun around 12:30 a.m. in Bakersfield, Calif. When a witness pointed to Francisco Serna, who was standing in a neighbor’s driveway, one officer fired and killed him, Bakersfield police spokesman Sgt. Gary Carruesco told CBS Bakersfield affiliate KBAK-TV.

No gun was turned up in a search of the scene, Carruesco said.

“Right across the street is where the police shot my father with nine bullets to his body,” a man the Los Angeles Times identifies as Rogelio Serna says in the video. “My dad was not armed.”

Carruesco said in an email to CBS News’ Crimesider he can’t yet say how many times Francisco Serna was struck or how many rounds the officer fired, but said his son is “misinformed.” A coroner was expected to complete an autopsy to determine a cause and manner of death.

Carruesco was awaiting interviews with officers to be completed before releasing more information to the media.

Rogelio Serna told the paper his father had been suffering from delusions and other early signs of dementia that had appeared to be getting worse in the past month. His father often took late-night walks alone to tire himself out, he said.

Serna’s son said his father had worked at a cotton gin in California’s Central Valley until retiring about a dozen years ago.

“My dad did not own a gun. He was a 73-year-old retired grandpa, just living life,” Rogelio Serna told the Los Angeles Times. “He should have been surrounded by family at old age, not surrounded by bullets.”

Family told KBAK-TV that Serna lived with his wife and one of their daughters.  

Police had visited the house twice before because his confused father activated a medical alarm, Rogelio Serna said.

Officials told KBAK-TV that the officer who shot Serna is on administrative leave. Their name has not been made public at this time.