Just months after being hired by District Attorney George Gascón to investigate officer-involved shootings, Roger Guzman has resigned amid accusations of off-duty misconduct.

The retired Los Angeles police detective was hired in November at a salary of $116,000 a year — part of a team Gascón assembled after a string of officer-involved shootings raised questions about police use of deadly force.

In April, Guzman was picked up on suspicion of public drunkenness after attending a training session for D.A. investigators near Sacramento. When word of his arrest reached his bosses in San Francisco, Guzman was removed from the specialized unit and handed other investigative assignments.

Alas, there was more trouble to follow.

According to court documents, a former girlfriend obtained a temporary restraining order against Guzman last week for alleged acts of domestic violence.

After San Francisco law enforcement was alerted, Gascón’s office referred the case to police agencies in the Los Angeles and San Diego areas for investigation, sources say.

We’re told Guzman submitted his resignation Tuesday, a day before he was to be called in to be fired.

D.A. spokesman Alex Bastian declined to comment, other than to say that Guzman “no longer works here.”

Guzman could not be reached for comment.

San Francisco Chronicle columnists Phillip Matier and Andrew Ross appear Sundays, Mondays and Wednesdays. Matier can be seen on the KPIX TV morning and evening news. He can also be heard on KCBS radio Monday through Friday at 7:50 a.m. and 5:50 p.m. Got a tip? Call (415) 777-8815, or email matierandross@sfchronicle.com. Twitter: @matierandross