PHILADELPHIA (CBS) — The video is disturbing. The reason behind the attack, perhaps horrifying.

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

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Investigators say the seemingly random and unprovoked attack happened Friday evening on the 700 block of Adams Avenue in the Lawncrest section of the Northeast. The victim was 30-year-old Mardoquo Sincal Jochola. He and his brother have been in the U.S. for eight years and are from Guatemala.

“Only he’s my brother,” said the victim’s brother. “Now, he really leave me forever. I never see him never ever.”

The victim’s brother, who said he’s afraid to show his face while the attackers are still out there, told Eyewitness News that his brother would work landscaping jobs and while they had very little here, they did have each other. “I want to go back to my country. I don’t want to live here no more,” he said.

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Police say it was just one sucker punch to the head that killed Sincal Jochola. He stumbled, hit the ground and the group, not even waiting a moment, runs away.

Detective are now looking into if this brutal attack could be part of that knockout game, where people are unsuspectingly punched, or hit on the street. “It certainly is a possibility, but regardless of what the motivation is, it’s still a pretty scary crime that some person could be walking down the street and be punched for no reason and killed,” said Lt. Riehl.

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Anyone with information on the attack is urged to call police.