Montana's Democratic governor on Friday ordered the release of Barry Beach, whose cause drew widespread support as he maintained his innocence throughout three decades in prison for the killing of a high school classmate.

Beach, 53, has been serving a 100-year sentence in Montana State Prison for deliberate homicide in the 1979 beating death of Kimberly Nees, 17, on the Fort Peck Indian Reservation, in the northeast corner of the state. His release was effective at noon.

Bullock noted in his order that Beach was a 17-year-old juvenile at the time and exhibited good behavior in prison.

"Obviously we're thrilled. It's going to get Barry home in time to be with his mom for Thanksgiving," said Beach's longtime attorney, Peter Camiel.

The murder of honor student Nees gripped the small town of Poplar after her body was found alongside the river at a popular place for teenagers to party. The killing remained unsolved for several years, with small-town gossip building until out-of-state police got Beach's confession after picking him up on an unrelated crime.

But Beach said his 1983 confession to Louisiana authorities was coerced. His long campaign for freedom drew support from hundreds, including Democratic U.S. Sen. Jon Tester, former Gov. Brian Schweitzer and former Republican U.S. Sen. Conrad Burns.

Bullock last year asked the state parole board to consider whether Beach served enough time in prison. State officials rejected Beach's request for clemency on four prior occasions. Last month, after receiving a fifth request, the state parole board forwarded the matter to Bullock.

A new law -- inspired in large part by Beach's case -- gives Montana's governor the final decision in clemency requests instead of the parole board.

Under the clemency order, Bullock commuted Beach's sentence to time served with an additional 10 years suspended, during which Beach will be on probation and supervised by the state Department of Corrections.

Beach was released for 18 months beginning in 2011 after a state judge ordered a new trial based on witness testimony that Nees died in a fight among a gang of girls.

But the state Supreme Court blocked that trial, sending him back to prison.

During his time on the outside, Beach worked at the Clocktower Inn in Montana's largest city, Billings, where his mother, Bobbi Clinch, lives.

Clinch said Friday the hotel's owner told her the job was still available for Beach, and she expects he will resume working there soon.

"He probably would like to take a little bit of time off, but there's the reality that he has to support himself," Clinch said.