A group of hackers obtained uncensored footage from inside the notorious Iranian Evin Prison, located in Tehran, reports the Associated Press and Radio Free Europe. The videos, some of which appear to be taken directly from the prison surveillance system, show squalid conditions, guards beating prisoners, and the moment when hackers seized control of the facility’s computers as baffled officials could only stand and watch.

The group responsible for the hack, which goes by the name The Justice of Ali, shared the videos with the AP and Radio Free Europe. They told the former that they’d obtained hundreds of gigabytes of data.

Iranian officials confirmed on Twitter that the stolen footage is real.

In one unforgettable moment among many, the stolen video shows prison computer screens going offline, one by one, only to then be replaced by a message from the hackers.

“Cyber attack,” cybersecurity journalist Kim Zetter reports the message as reading in Farsi. “Evin is a stain on the black turban and white beard of Iranian President Ibrahim Raisi – the nationwide protest [will continue] until the release of political prisoners.”

Tweet may have been deleted

One prison official appears to take video of the hacked system, as another looks on — for all appearances at a complete loss.

While it’s not clear exactly how, specifically, the footage was obtained, Zetter explains that “Iranian systems often use bootleg or out-of-date software, due to sanctions that make it difficult to keep systems up to date.”

Notably, the hackers claim this is just the beginning of their efforts. “We will continue to expose the oppression,” Radio Free Europe reports them as saying.

And, if the small amount of published video is any indication, there’s a lot of oppression to expose. The Evin prison has been described by former inmates as “the most brutal prison in the world.” Even before this footage was released, Evin was long known as a site where political dissidents were allegedly tortured.