A 29 year-old man claims he was attacked and bitten in the arm by an unidentified perpetrator as the Arctic Monkeys performed Friday evening at Lollapalooza.

David Lenet said he and a friend were victims of an unprompted assault at the festival in Chicago's Grant Park, according to the Chicago Sun-Times. Lenet detailed the incident on Reddit. "The mood of the crowd is really happy and a nice departure from the normal drunken debauchery," he wrote. "Suddenly, I turn around and some guy none of us have ever seen or spoken to, without warning, body slams my friend and begins using his hands to choke him."

Lenet said he and his friends began fighting back, but as he tried to pull the assailant away, he was bitten on his arm for about five seconds. "He's not biting me," he told the Sun-Times. "He’s clearly trying to bite through me." Lenet posted graphic photos of the injury here.

The attacker allegedly withstood 10 to 15 punches and kicks to the head, and eventually walked away seemingly uninjured, prompting Chicago police to report he may have been on PCP or bath salts. Lenet said on Reddit, "No one stopped him because everyone was shocked by the hole in my arm, and I don't think anyone had much interest in trying to apprehend the dude who just took 10 punches and a punt to the face from three big dudes ... and walked away."

Lenet was treated at a festival medical tent and was placed on an anti-HIV cocktail because the bite broke the skin.

The attacker is described as a dark-skinned man between 5'7" and 5'11," between 170 and 210 pounds. Police said they had nobody in custody regarding the attack.

Here's video of the Arctic Monkeys performance that provided the backdrop:

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