AUGUSTA — An Augusta man who made a silencer for his rifle out of an automotive oil filter pleaded guilty to possessing an unregistered silencer Tuesday in federal court in Bangor.

Ryan D. Merrill, 39, was firing a .22-caliber rifle at a fox and small propane tanks behind his home on Holly Hill Lane when Augusta police responded to a complaint of gunshots in a residential area on July 17, 2018, according to a news release from U.S. Attorney Halsey B. Frank.

Officers discovered that Merrill had modified an automotive oil filter and attached it to the muzzle of the rifle using a special adapter, to suppress the sound of the rounds he fired. The silencer had not been registered with the National Firearms Registration and Transfer Record and, the release said, and Merrill knew that the possession of the silencer was prohibited by federal law.

Merrill was indicted in October 2018.

The charge is punishable by a fine of up to $10,000 and 10 years in prison. Merrill has not been sentenced yet.

An entry in the Augusta police log after the incident indicates that Merrill was issued a summons on a charge of discharging a firearm within city limits after suspicious activity was reported July 17, 2018, on Holly Hill Lane. On Sept. 10, 2018, he was fined $50 at the Capital Judicial Center in Augusta for that civil violation.