An off-duty New York City firefighter was arrested and charged with assaulting his girlfriend and her two grown kids, police said Saturday.

Randy Beckford, 49, attacked his 43-year-old girlfriend in their Brooklyn home late Friday, allegedly choking her before her two adult children intervened, authorities said.

Beckford allegedly got physical with the woman’s 25-year-old son and 21-year-old daughter when someone called police to break up the fight, police said.

Beckford, who has worked for the FDNY since at least 2008 and earned over $112,000 last year, was charged with two counts of strangulation and one count of assault, the NYPD said.