BURLINGTON — A convicted murderer in Vermont has been released from prison for the first time in 21 years.

Douglas Mason left the federal court in Burlington on Thursday as a free man.

The 43-year-old Mason was convicted in the 1991 fatal stabbing of John Irons at a Barre motel.

The Burlington Free Press reported that the state Corrections Department had concerns about releasing Mason because of his lack of involvement in treatment or rehabilitation programs. Mason completed his state sentence May 15.

In 1995, he received a three-year sentence for sending a judge a threatening letter. Prosecutors tried last week to extend Mason’s sentence because of confusion over whether had served that time.

Mason will need to report to a probation officer. He said he’s a changed man.