Michael Bowden, 18, is accused of taking a picture holding the weapon and ammunition outside a Walmart in the state, posting it on Snapchat and sending it to an employee at the store.
He captioned the post: “Lewiston Part 2.”
The Somerset County Sheriff’s Office said it took action over Mr Bowden’s Snapchat post after receiving a report about the photograph, which is believed to have been taken outside the store in Palmyra, Maine.
“He took a picture of himself in a vehicle in the Walmart parking lot, and in that picture you can see a gun – a hunting rifle,” Chief Deputy Mike Mitchell told The Portland Press Herald. “You can also see a bullet in his lap.”
“They were communicating back and forth through Snapchat messaging, and (the employee) basically said, ‘What is this?’”
And he added: “We take this stuff very seriously. You have to nowadays.”
Prosecutors said that Mr Bowden is a former employee at the store but was fired in 2021.
He has recently been regularly seen in the store’s car park, including on Saturday night, police said.
The suspect was arrested at his home in Etna without incident and was charged with aggravated reckless conduct and domestic violence terrorising.
The gun in the picture was a Savage bolt action hunting rifle and it was seized as evidence in the case, the sheriff’s office said.
Mr Bowden was booked into the Somerset County Jail and later released on $10,000 cash bail. He will appear in court on 3 January 2024.