BOSTON (AP) — In a photo he posted on Twitter, Kwmaine Davis had a big smile on his face as he held one gun in each hand at a shooting range. His message to his followers: “Yes, I’m really bout that action.”

What Davis didn’t know is that one of his followers was a Boston police officer.

As a convicted felon, Davis isn’t allowed to possess guns, even if he’s only shooting them at a firing range. A federal judge sentenced him Wednesday to 18 months in prison for doing just that.

After seeing two firing range photos Davis posted on Twitter, Boston police notified federal authorities. Police were concerned that Davis, a known member of a violent Boston gang, had gone to the firing range to perfect his shooting skills. He already had been shot twice himself and convicted once before for illegal possession of a gun.

When confronted by police with the Twitter photos, Davis agreed to plead guilty to being a felon in possession of a firearm.

He was sentenced to prison after saying he accepted responsibility for his actions and wanted to turn his life around. Davis, 23, told U.S. District Judge Denise Casper that he plans to go to counseling, return to school and find a job after his release.

Casper imposed a sentence that was agreed to by prosecutors and Davis’ lawyer under a plea deal. The judge told Davis she hopes he will make an “earnest effort” to get his life on track.

“At the end of the day, it’s up to you, and I wish you good luck,” she said, just before Davis was led away to begin serving his sentence.

Davis’ lawyer, Joshua Hanye, said his client admitted to being a member of the H-bloc gang — a violent gang that operates in Boston’s Roxbury neighborhood — since the age of 13. But he said he Davis is “ready to make a change.”

Hanye pointed out that using guns at a shooting range “is legal and safe” for most people and that David did not take the guns with him when he left.

“Since his arrest, he’s done everything he can to show he wants to make a change,” Hanye said.

Assistant U.S. Attorney John Wortmann Jr. said Davis signed an indemnification agreement at the Salisbury shooting range that included a warning that federal and state regulations prohibit the possession of a gun by anyone convicted of a felony.