SAN FRANCISCO (CBS SF) — San Francisco police have made an arrest in a vicious attack on a homeless man that was caught on camera in the Tenderloin District earlier this week.

According to police, 36-year-old Arthur Lee Jones of Fairfield was arrested on suspicion of attempted murder and aggravated assault.

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Police say the victim was sitting on a stool on Geary Street Wednesday night near the Gangway Bar when the attack occurred. Surveillance video shows a man approaching the victim and hitting him in the head with a pipe.

(Warning: disturbing images)

“The victim wasn’t expecting anything to happen, and then suddenly he was assaulted,” said Officer Carlos Manfredi of the San Francisco Police Department.

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The victim suffered a severe injury that required 50 stitches to close and remained hospitalized on Friday.

Following the attack, the bar owner tried to help the man, who people only know as “Robert.”

“I let him use my restroom, I treated him — you know, I gave him a couple of bucks when he asked me — I give him a drink,” said owner Jung Lee. “He’s a good guy. You know, he’s homeless. But he doesn’t start trouble.”

A building manager who knows Robert visited him in the hospital last night and said he was up and talking.

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Police believe the attack was planned because cameras captured the suspect casing the scene.