Location of imprisoned Colorado theater shooter finally revealed by authorities

— -- Authorities with the federal prison system revealed overnight that convicted mass murderer James Holmes, serving multiple life sentences for a 2012 massacre at an Aurora, Colorado movie theater, is now being held at a maximum-security penitentiary in Pennsylvania.

As of 5 a.m. Thursday, Holmes is serving his time at the Allenwood prison, west of Wilkes Barre, Pennsylvania.

The location where Holmes was being kept had become the source of major controversy since his trial and sentencing in 2015. Holmes was moved to a prison outside Colorado in late 2015 after he was attacked in a minor incident at a lockup. Corrections officials in Colorado refused repeatedly to say where Holmes was being held and offered differing rationales for the secrecy.

Family members of victims waged a lengthy public battle against the state, seeking information on Holmes' location and the murderer's transfer had become a key issue in the campaign for governor.

"It's been a long time coming," Caren Teves, whose son Alex was gunned down at the opening night showing of "The Dark Knight Rises" at Century 16 Theater, said of the fact that Holmes' location is now known. "Why should that monster have the right to privacy? My son's rights were completely taken away when he was murdered."

The shooter was moved to a new location after he was attacked at the Colorado State Penitentiary in Canon City in 2015. The Colorado Department of Corrections explained at the time that they moved him for safety reasons, though records obtained by ABC News at the time showed the incident to be minor and the result of mistakes by prison personnel.

At various times, Department of Corrections officials said the move and need for secrecy was for Holmes' safety, the safety of prison personnel, the safety of other prisoners and even rules they could not control.

After the transfer, Teves and other victims’ families fought unsuccessfully to learn of the killer’s location. When the Colorado Department of Corrections (CDOC) denied them the information, they took their case to Colorado’s Victims’ Rights Subcommittee which voted not to force the CDOC to reveal the killer’s whereabouts.

Arapahoe County District Attorney George Brauchler, who sought and failed to get the death penalty for the now 29-year-old prisoner, has been frustrated with the fog surrounding the shooter's whereabouts.

"I want the victims to know a certain peace in learning where he’s housed. That brings me great relief on their behalf," he told ABC News.

The killer's location was kept secret right after his sentencing and was then made public briefly. Officials have refused to say where was being held since his move out of state in January 2016.

Next month, Holmes' parents, Bob and Arlene Holmes, will participate in a symposium at Penn State's Beaver campus to discuss the possible link between mental health and violence. That event will be held about 250 miles away from the prison where Holmes is now locked up.

Holmes is serving 12 life sentences plus an extra 3,000 years for murdering 12 and wounding 70 others on July 20, 2012. His official sentence discharge date is listed as Dec. 31, 9998.