A chronically violent felon has received a term topping 18 years for the beating of a security staffer working in the state's sex offender treatment facility in Moose Lake.

Nicolas L. Aron-Jones, 29, was sentenced Tuesday in Carlton County District Court after pleading guilty to second-degree attempted murder in connection with the unprovoked attack on May 1 at the Minnesota Sex Offender Program (MSOP) site.

With credit for time in custody since his arrest, Aron-Jones is expected to serve the first 12 years of his term in prison and the balance on supervised release.

The victim, a 53-year-old security counselor who was making his scheduled rounds at the time, suffered bleeding on the brain and a cut near his right eye during the ambush, the charges read. He was taken by air ambulance to a hospital for treatment. MSOP has not released his identity.

Aron-Jones was committed as a client to the program in 2015 as a sexually dangerous person and was housed in Omega 2, one of Moose Lake's more restrictive units.

Court records show that Aron-Jones has numerous convictions for violent outbursts at the Moose Lake facility: In June 2020, he was handcuffed while he kneed and bit a staff member; in March 2019, he put a hairbrush in a sock and swung it at things, damaging windows and yelling death threats at staff during a 20-minute tirade; in June 2017, he punched and kicked a security counselor into unconsciousness; in May 2016, he spit at and attacked a security counselor, broke a table and threw a chair at a television.

According to the charges related to the latest assault:

Aron-Jones swung a pillowcase holding a motor for a fan and hit the counselor in the back of the head. The man fell to the floor and Aron-Jones struck him with the motor several more times to the head and elsewhere. Aron-Jones then kicked and stomped on the victim's head.

Other staff intervened, spraying a chemical irritant at Aron-Jones, who retreated to his room and closed the door.