Demi Lovato‘s ex-fiancé’s mug shot is out … along with new details from cops about his arrest — with his own mother accusing him of abusing nitrous oxide and roughing her up in public.

Florida’s Port St. Lucie Police Dept. released the photo Thursday … capturing Max Ehrich‘s tight-lipped countenance and furrowed brow.

We broke the story … Ehrich was arrested Tuesday for battery on a person 65 or older. He posted $1,000 bond, and he was released Wednesday.

Cops have also released more details from the arrest … with officers claiming they got a call from someone who alleged Erich was live streaming himself beating on his mother.

According to the report, cops spoke to Erich’s mother … and, they say she told them Max “heavily abuses inhalants” and had consumed nitrous oxide on Tuesday before allegedly becoming violent during an argument about her phone.

Cops say Ehrich’s mother told them he chased her into a neighbor’s yard, shoved her to the ground and kicked her in the leg. However, officers say she refused to have her injuries photographed or provide a written statement.

Authorities say they took Ehrich into custody after several minutes of attempting to get him to exit the home. The documents say he will be “Baker Acted” — which is Florida’s legal way of putting someone on a psychiatric hold for further evaluation.

Ehrich was very briefly engaged to Demi Lovato back in 2020 … popping the question after just four months of dating in July 2020. However, the two split for good by the end of September.