The Aurora theater shooter has been transferred to a federal prison in Allenwood, Pennsylvania, according to the Federal Bureau of Prisons website.

A letter, sent to the victims’ families by the Colorado Department of Corrections on Wednesday, indicated the shooter's location would be released to those families for the first time since he was transferred out of state.

According to a DOC release, Colorado wanted to transfer the shooter into a federal facility several months ago. The release says they had to wait for space at a prison with "appropriate" security to open. An opening recently became available and the transfer was secured.

The Department of Corrections declined to provide the location of the Aurora theater shooter to the victims’ families when he was first transferred out of state in the summer of 2016.

That transfer happened partly because he was attacked by another inmate, according to documents released about the assault in March of 2016.

At that time, some Aurora victim families requested information about his whereabouts. That request was denied.

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Those families argued they have the right to know the location of the person who caused their devastation, based their interpretation of the Colorado’s Victim Rights Act. According to one section of the law, if a victim requests the whereabouts of an inmate in writing, the DOC "shall" provide the institution where the inmate is being held.

In May, 9Wants to Know asked the governor’s chief legal counsel Jacki Cooper Melmed if the Victim Rights Act prohibits the governor from telling the victims the location of various inmates transferred out of state.

"In this case, it doesn’t prohibit or require," Cooper Melmed said.

She said the law only requires DOC to notify the family if the inmate is being transferred to a lower security facility or if the move is permanent, not temporary. In their letters to victims, DOC says the prisoners have been "temporarily transferred," and therefore their locations will not be disclosed.

As of March 2017, 116 Colorado prisoners were serving their time elsewhere as part of this prisoner swap system according to state records obtained by 9Wants to Know.

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The letter sent to victims' families about the most recent transfer does not indicate a reason for the move. The DOC sent a press release Wednesday night that also does not include that information. They told 9NEWS they would not be commenting on the reason for the shooter's transfer.

9NEWS also reached out to the DOC on Wednesday asking them questions about whether the DOC is paying for the shooter's housing in the federal system and the conditions of his confinement.

Here's what we received from DOC Spokesperson Mark Fairbairn Wednesday in response to these questions:

Is the DOC paying for his housing in the fed system?

Holmes is being housed in the FBOP under the Interstate Corrections Compact.

What are the conditions of his confinement?

FBOP is housing Holmes in a high security facility that ensures protection of the public , staff and offenders. We can not speak specifically to the conditions of confinement at the facility.

Fairbairn went on to say that the mass murderer was moved "for the best interest of the public, staff and offender" but didn't elaborate. There was no money exchanged when it came to the shooter's transfer from the undisclosed location to the federal prison.

According to Fairbairn, the DOC can't disclose how the shooter was transported from one prison to another, or who paid for that.

Read the full letter:

Emily Tofte Nestaval, the executive director of the Rocky Mountain Victim Law Center, called the notification "the least victim-centered" and the "least-trauma informed" notification she's ever seen.

"So not only did victims receive this letter, not only out of the blue after months of being denied this information, but to receive this saying he's been moved, but we aren't going to tell you until the middle of the night, essentially?" she siad.

"So the victims had to sit with this information and anxiety, is he going to be moved to my backyard, is he going to be moved next to my relatives, perhaps children who are out-of-state, etc ...? ... really just it's traumatizing. It's really victimizing."