Legal Question in Criminal Law in California

Aside from the obvious about being fired..

Your coworker could file a police report that could lead to criminal charges - anything from simple misdemeanor battery up to attempted murder, depending on how badly you beat him and what your intent was. Even a battery charge would mean you would lose your right to have a firearm for 10 years and could face jail time, probation, etc.

He could also sue you civilly for any damages, including pain and suffering.

You can be charged with assault and, of course, can always be pursued civilly, by the victim. But your concern should be the criminal charges. David Wallin

It appears you never learned that there are consequences to your behavior. You face potential criminal charges, civil lawsuit for damages, and termination of employment.