A 46-year-old plumber was arrested on homicide charges after police say he picked up a steel gym bar at a Bally's Total Fitness and attacked another club member, striking him on the head "several times" before dropping the piece of equipment and leaving the scene.

South San Francisco Sgt. Tom Neary told NBC Bay Area that Kenneth Osako picked up a steel bar, similar to one from a lat pull-down machine, and struck the other gym member with a fatal blow at about 9:30 p.m. Wednesday night.

The San Mateo County Coroner identified the gym member as Diego Galindo, 43, of San Bruno.

Galindo was taken to San Francisco General Hospital, where he died on Thursday from his injuries, police said. Also on Thursday, a team of officers arrested Osako at a plumbing job site in San Francisco on Kansas Street, after he agreed to surrender, Neary said.

It was unclear if Osako was represented by an attorney. A legal representative for Bally's did not return a phone call on Friday. Osako declined a request for a jail-house interview.

Osako, whose mug shot shows an eye piercing of a barbell, was booked into San Mateo County jail on charges of murder. He was not allowed bail.

San Mateo County Assistant District Attorney Karen Guidotti said on Friday morning that her office did not yet have the police report, and the earliest Osako would be in court would be on Monday.

Neary said investigators were interviewing people to figure out a motive and whether Osako and Galindo knew each other. There were several witnesses in the gym who saw parts of the attack, police said.

A co-worker of Galindo's at Carneceria Pepa said Galindo and Osako knew each other only in passing, and he described Galindo as a friendly guy, who liked cars and motorcycles.

The suspect's father, Kenneth Osako Sr., said his son was a good kid. He showed NBC Bay Area his son's room, which was filled with different over-the-counter prescription pill bottles and fitness supplements.

"I just hope he gives us a call and let us know what happened," he said.

When asked if he would support his son either way, Kenneth Osako Sr. said "No, if he's guilty, he's guilty. I don't support anybody that's wrong."

On Friday, it appeared to be business as usual at the gym at 180 El Camino Real. Some members didn't even know about the brutal attack less than 48 hours before hand.

"My trainer acted like nothing had happened," Carlos Sosa Jr. told NBC Bay Area.

NBC Bay Area originally incorrectly identified the weapon as a barbell. Neary said Friday that the piece of gym equipment was "a weapon of opportunity."