Two people were killed and two others were wounded early Monday when shooting erupted inside a vehicle traveling downtown on Michigan Avenue, police said.

Five men were inside the car just after midnight as it traveled south in the 500 block of South Michigan, according to Chicago police spokesman Al Stinites.

“Something happened inside the vehicle — we’re not sure what yet — causing shots to be fired inside the vehicle,” Stinites said.

The driver was shot in his shoulder and lost control of the car, which then crashed into a pole and flipped on its roof.

Four people were taken to hospitals with gunshot wounds, and two of them were pronounced dead shortly after, Stinites said. A fifth person was also taken to a hospital to be “checked out.”

Bruce Y. Miller, 29, of the Jeffrey Manor neighborhood, suffered a gunshot wound to the head and was taken to Northwestern Memorial Hospital, where he died at 12:37 a.m., according to Chicago police and the Cook County medical examiner’s office.

Steve Nixon, 31, of the Chatham neighborhood, was also taken to Northwestern after being shot in the face, authorities said. He was pronounced dead at 12:39 a.m.

Chicago police investigate a scene where four people were shot Monday morning in the 500 block of South Michigan Avenue. | Tyler LaRiviere/Sun-Times

Among the wounded were two other 29-year-olds who were both shot in their shoulders, police said. Their conditions were stabilized at Northwestern and Stroger Hospital, respectively.

A 39-year-old who wasn’t shot was taken to Stroger with back and neck pain from the crash, according to police.

Stinites said the shooting was limited to the people inside the car and that no one else was harmed. After the car flipped over, one person suffering gunshot wounds ran from the car into the nearby Congress Plaza Hotel.

A delivery driver who witnessed the immediate aftermath of the shooting from inside the hotel said he saw two men enter the building with large assault rifles.

“There were three security guards for Congress Plaza Hotel who stopped those two guys from running in,” Sayed Mahmoodi, a driver for GrubHub, said. “One was bleeding from his hand; the other one was carrying an AK-47 and an AR-15.”

“I was f—— scared, man, after seeing those big f—— guns,” Mahmoodi said. “I never thought I was going to see something downtown — not in my life. I’ve seen shootings before, but not like this.”

Officers showed up within minutes of the crash and secured the scene, Stinites said. Two weapons were recovered.

Police were unsure who in the car fired the shots and said the victims were giving conflicting accounts of the incident.

No one was in custody early Monday as Area Central detectives investigated the shooting, police said.