CHICAGO (CBS)—Police are searching tonight for the gunman who fatally shot a man who stood up for a bicyclist who was hit by a driver last night in the Greater Grand Crossing neighborhood.

The man who was killed, Alberto Bocanegra, went live on Facebook while driving behind a group of cyclists on a late night ride. Police said Bocanegra, 39, was driving near 76th and Eberhart around 1:30 a.m. Tuesday when he saw a car hit a 30-year-old woman on her bike and then flee the scene.

Police said Bocanegra caught up with hit-and-run driver and got into an argument with the people in that car. Those people apparently called a third driver, who pulled up in a blue SUV and shot the man twice in the neck.

alberto bocanegra Friends Remember Man Murdered After Stepping In To Help Cyclist

Alberto Bocanegra was shot and killed on Sept. 25, 2018, after confronting a hit-and-run driver who had struck a bicyclist. (Photo supplied to CBS)

“I tried to stop them, and calm it down. It looked like everybody was calming down, and then the guy with the gun killed the guy in the car,” said one of the bicyclists, who asked to remain anonymous. “It was calm. They were calming down, but because he had a gun, he just had it as though he, in his mind, he was like, ‘Oh, forget it. I’m just gonna follow through.”

Family friend Frank Avila said Bocanegra had a “heart of gold.”

Another family friend, William “Dock” Walls said Bocanegra never hesitated to help others.

“Alberto was always coming to someone else’s defense,” Walls said. “It didn’t matter if they were white, black, Latino or Asian, he just loved human beings and he was there as a protector.”

Early this morning, Bocanegra confronted the driver who hit the cyclist, triggering a verbal argument.

The dispute escalated, quickly turning physical before the person in the SUV pulled up and shot him.

Friends remembered Bocanegra Tuesday for his bravery, with one saying he’s seen him confront gang members in the past.

Bocanegra’s death follows a battle with blood and bone cancer, his family says.

No arrests have been made.