Chicago (CBS) — The city of Chicago lost an officer, and Julian Martinez lost one of his best friends. He says he met John Rivera in the first grade. They grew up together on the Far South Side in Hegewisch.

“He was the last person in the world to deserve this,” Martinez said. “All I keep asking myself is, ‘Why? Why him?’ He would never do anything. He was the perfect person.”

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Chicago police say Rivera and his friends had left a bar in River North Saturday morning and were sitting in a car around 3:30 a.m. Investigators say two men approached the car near Clark and Huron Street and at least one of them started shooting.

“This appears to be a unprovoked attack against a group of individuals who went out to unwind on a Friday night,” Chicago Police Supt. Eddie Johnson said.

Sources say two groups were fighting in River North. People from one group went looking for people from another group, and they stumbled upon Rivera and his friends. According to sources, the shooter may have thought Rivera was someone else.

Hegewisch barber Neko Castillo says Rivera was a friend who wouldn’t hurt a fly.

“One of those situations where some people ask, ‘oh, do you think he could have been having altercations with anybody?’ From my point of view from knowing him, I don’t think so,” Castillo said.

Police say Rivera had just wrapped up a shift around 10 p.m. Friday.

Martinez says he’s also friends with another off-duty officer who was in the car and was not shot. He says he was planning on going out with the group, but his girlfriend felt sick.

“I probably would have been in that car with them and God knows where I would be right now, whether dead, shot, still alive or traumatized,” Martinez said.

Martinez says he’s also friends with another person in the car who was shot. He says that person is up and talking, but still at the hospital.

Police say they are questioning one person, who is not a suspect. They’re also reviewing security video.