PORTLAND, Ore. (KOIN) – A 43-year-old man who allegedly killed a young bull moose on the Umatilla Indian Reservation was arrested by the FBI for unlawfully possessing an unregistered short-barreled shotgun.

Thadd Justin Nelson was indicted by a grand jury on the gun charge. Prosecutors said he had a weapon made from a West Point Model 949, 20-guage short-barreled shotgun, with a barrel length of 16.5 inches, and was not registered to him in the National Firearms Registration and Transfer Record. FBI spokesperson Beth Anne Steele on Friday confirmed the arrest, but could not provide additional details because of the on-going nature of the case.

Investigators found Nelson with the weapon on Feb. 11, 2015, court records show, and the Umatilla County DA filed charges for violating state wildlife laws the next day. The records in the still-pending case show the animal was killed around June 1, 2014.

According to the East Oregonian newspaper, Nelson was arrested Feb. 10, 2015 after an investigation involving the Pendleton Police Department, Blue Mountain Enforcement Narcotics Team, FBI and the Umatilla and Morrow County Sheriff’s Offices. The paper reports Nelson killed a young bull moose last summer near his home on the Umatilla Indian Reservation.

In addition to the head, hide and remains of the moose, police recovered two stolen vehicles, an ATV and a handgun, the paper reported. Drugs, an illegal short-barreled shotgun and the hunting rifle allegedly used to kill the animal were also recovered, the paper reports.

Court records show Nelson is charged in Umatilla County with chasing or harassing wildlife and wasting the remains of wildlife.

A spokesperson with the United States Attorney’s Office on Friday was unable to provide additional details on the new federal case.