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A Philadelphia man, accompanied by two friends, sucker punched an unsuspecting guy at random and killed him.

That’s what police believe.

The suepect, “all of a sudden, without any notice, throws a punch and it’s clear the victim never saw it coming,” Lt. Phillip Riehl of the Philadelphia Police said on the video.

The victim was 30-year-old Mardoquo Sincal Jochola. He and his brother came to the U.S. eight years ago from Guatemala—a place, the victim’s brother says, he wants to return to.

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“Only he’s my brother, now, he really leave me forever. I never see him never ever,” said the victim’s brother. “I want to go back to my country. I don’t want to live here no more.”

In the video, Jochola takes one punch to the head, stumbles for a moment, then falls to the ground while the young men take off running.

Police suspect the killing may have been a part of a violent Knockout Game where a person is chosen at random and punched or hit in the head. The game has gained some traction among kids and young adults lately.

According to the CBS Philadelphia video, the police are still searching for the three suspects.