NEW YORK (CBSNewYork) — Police are warning the public about attacks on the Upper West Side as they search for four suspects.

“He came up and asked if he looked bad, and he did,” said Jessica Rieske.

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Rieske told CBS2’s Ilana Gold the man caught her off guard just after 11 p.m. Thursday when she was walking her dogs at Riverside Park.

“He was bleeding a lot from his head. He had been beaten pretty badly. The whole left side of his face was swollen,” she said.

Police said four men went after the 21-year-old man at 68th Street near the Hudson River as he was on his way home from John Jay College.

“It was scary, and I just felt terrible for him. He was all alone and young and really scared,” said Rieske.

The suspects threw a bag over his head, beat him with some sort of object then stole his phone, wallet and laptop, Gold reported.

“I walked him home and we got him an ambulance and then the police came,”  said Rieske.

Just an hour and a half earlier, police said they believe the same group attacked a homeless man on a park bench at 73rd Street.

A neighbor who didn’t want her face shown on camera said she found the homeless man in the river the next morning.

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“I see a man whose feet are submerged in the river, who’s clinging to the wall to stay above water,” said one neighbor, who didn’t want her face shown on camera.

Investigators said the attackers threw him over the guard rail.

“He didn’t seem capable of even asking for help. This man was clearly freezing cold,” she said.

Right now, police are stepping up patrols in the area, especially at night, to make sure these culprits don’t strike again, Gold reported.

“We haven’t seen incidents like this for years,” said councilor Helen Rosenthal.

Police are also posting signs offering a $2,000 reward around the area of the attack, hoping someone knows who is responsible.

“There’s a certain level of viciousness involved in an activity like that. That’s just incomprehensible,” said one woman.

Both victims were treated at a hospital. The 21-year-old has been released, but there’s no word on the condition of the homeless man.

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