One Florida teen learned the hard way not to do it for the ‘Gram, police said.

Moses Clay Jr., 17, was arrested Saturday by the Boynton Beach Police Department after investigators said he stole an AR-15 and other weapons from an unmarked Palm Beach County Sheriff’s Office police vehicle and later “bragged about having it” during a video on Instagram Live.

Clay was arrested after an officer and his K-9 partner, Iro, found the stolen weapon beneath his mattress, Boynton Beach police announced on Facebook.

“It is unfortunate, yes, but law enforcement officers are human beings and forget to lock their car doors sometimes too,” department officials said. “Fortunately, our detectives were able to quickly identify the suspect and get the firearm out of the hands of a criminal.”

A cop in Boynton Beach made the find after getting tipped off to the Instagram video, WPLG reports.

The deputy in Palm Beach reported the theft to Boynton Beach police after leaving his car at a shopping center parking lot on Tuesday, according to records obtained by the Miami Herald. Other items stolen from the vehicle included two loaded magazines, a gas mask, a Taser and a ballistic helmet, according to the newspaper.

Clay, who has been charged with grand theft and burglary while armed with a firearm, was taken to a juvenile detention center, the Herald reports.

Some Facebook users, meanwhile, took issue with the department’s Facebook post, taking several shots at the #OneLessGun hashtag accompanying a photograph of the allegedly stolen AR-15.

“All this talk about guns stolen from cars and this was an agency gun lost from a police car?” one user wrote.

Another man said he thought there was “no excuse” for the deputy who left his unmarked car unlocked, calling it a lapse of judgment.

“This could have turned out much worse if someone was killed with that firearm,” the user replied. “The officer responsible for the firearm deserves to be held accountable for the theft of this weapon. I would be!!!”

Teri Barbera, a spokeswoman for the Palm Beach County Sheriff’s Office, told The Post that an internal review into the actions of the deputy — who has not been publicly identified — is ongoing. He could face disciplinary action, she said.