Philadelphia police have four boys in custody in an attack on an intellectually challenged man that was caught on camera and posted to Facebook.

Facebook has since taken the video down, but it is still available on several websites. Click here to see it, but a warning, it's disturbing and graphic.

Gerald Andrews Sr. shared the footage.

“This guy is a friend of mine who happens to be mentally challenged,” Andrews said.

The slow-motion video showed the boys, two of them throwing punches at the man, as the other two watched and laughed.

According to Andrews, the victim is named Mark Smith, 38, and is one of his coworkers.

“He keeps that smile on his face. He wants to talk sports. He’s a good guy,” Andrews said.

“It’s heartbreaking.”

A still from the video that was posted to Facebook, showing one of the suspects getting ready to sucker punch 38-year-old Mark Smith. Police have now caught the four boys accused in the attack. 
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The boys range in age from 12 to 15, according to ABC 7 New York.

"Obviously, what is depicted in the video is very disturbing," Philadelphia police Capt. Malachi Jones told ABC.

“It appears this male, who is 38 years old, was targeted because he is mentally challenged. It’s a senseless act of violence.”

Three of the boys were arrested at school Tuesday and released into the custody of their parents.

Two of the boys may have been involved in another attack case, police said.

No word yet on charges in the case.