A bullet fired by a security guard struck an innocent bystander during a chaotic series of events Friday along the Dan Ryan Expressway, but the guard was acting in self-defense and won’t be charged, Chicago police said Monday.

The 54-year-old man was shot in the ear shortly after 4 p.m. when the security guard fired the shot after someone pointed a gun at the guard following a crash, police said.

The incident unfolded minutes before with a report of gunfire near 43rd Street and Wentworth Avenue in Fuller Park.

A car involved in that incident — a Kia sedan — fled the scene, heading south on Interstate 94 before exiting at Garfield Boulevard, police said. That car, which had been stolen in a carjacking Thursday, then crashed into two other vehicles as it approached 55th Street. After the crash, as many as five people fled the scene, authorities said.

Employees of a private security company that works in the area saw the crash and followed the people who fled the scene. One of the people fleeing then pointed a gun at a security guard, police said.

The guard, “in fear for his life,” then fired his weapon, said officer Norma Pelayo, a police spokeswoman. But the bullet accidentally struck the bystander, who was in a car in a drive-thru of a nearby Wendy’s restaurant.

The wounded man drove to 54th and Halsted streets — nearly a mile from where the shooting took place — where he called for help, authorities said. He was taken to University of Chicago Medical Center, where his condition stabilized.

Police said he was not involved in the incidents that preceded the accidental shooting.

The security guard was not facing any charges and was also considered a victim in the incident, police said.

An assault-style rifle and handgun were recovered from the stolen car, police said. None of the people who fled the car had been taken into custody as an investigation into the incidents continued Monday.