Chicago, IL – Another Chicago police officer would have been seriously wounded or killed at Mercy Hospital on Monday if his gun and holster hadn’t stopped a bullet.

Three victims were murdered at the busy Chicago hospital after 32-year-old Juan Lopez opened fire on his former fiancé after asking her to return her engagement ring.

The shooting began after Lopez confronted Dr. Tamara O’Neal in the hospital parking lot at about 3:20 p.m. on Nov. 19 to ask for the ring back, WGN reported.

A witness told WGN that O’Neal, who had recently called off the engagement, told Lopez she didn’t have the engagement ring with her and the man she was supposed to have married started shooting.

Lopez shot O’Neal repeatedly, standing over her as he fired his last shots, witnesses said.

“Then once she fell to the ground, he stood over her and shot her three more times,” a witness said, according to WFLD.

When police arrived, Lopez engaged in a gunfight with them in the hospital lobby, the Chicago Tribune reported.

Chicago Police Officer Samuel Jimenez exchanged gunfire with Lopez, and was fatally shot.

“When they pulled up, they heard the gunshots, and they did what heroic officers always do — they ran toward that gunfire,” Chicago Police Superintendent Eddie Johnson told reporters during a press conference on Monday night.

It was during the gunfight from the entrance of the lobby that Lopez shot a police vehicle and another police officer.

The bullet struck the holster on the second officer’s belt, and lodged in the side of his pistol.

WGN posted pictures of the gun and holster that saved the officer’s life on Twitter on Monday night.

Had Lopez’s bullet hit just a fraction to the left or right of where it ended up, the officer wearing that holster would likely have been critically injured or killed.

Sources told the Chicago Tribune that Lopez had a concealed-carry permit for the weapon he used to kill his former fiancé and Officer Jimenez.

Pharmacy resident 25-year-old Dayna Less had the misfortune to step out of an elevator and into the lobby at just the wrong minute as Lopez was in a gun battle with police.

Less was shot, and then Lopez took off into the hospital, the Chicago Tribune reported.

Officers locked down the first floor of the hospital and the stairwells to conduct a search for Lopez and additional victims.

“We’re checking for victims,” a dispatcher said over the radio at that time, according to the Chicago Tribune. “We also need officers on the third floor to check the nursery.”

Lopez was found shortly thereafter, deceased with an apparent gunshot wound to the head.

It is not yet known whether Lopez died from a wound he received during the gunfight, or if the fatal shot was self-inflicted.

An emergency room clerk who worked with O’Neal said Lopez had called the emergency room looking for his former fiancé hours before he arrived with a gun.

“He called and asked to speak with his fiancé,” Steven Mixon told the Chicago Tribune. “And she said, ‘Oh, just tell him I’m in with a patient.’”

When Mixon finished work at 3 p.m., he called an Uber and went to wait for it out in front of the hospital.

“I look up and I see her being harassed by some gentleman,” he said. “She was trying to avoid him and move around. And when she saw me, she waved for me to come that way.”

Mixon started running toward O’Neal to help, but Lopez starting shooting at her before her friend got there.

“I guess it wasn’t my time to go because if I had made it to her, I would have been dead too,” he told the Chicago Tribune.

Police have not released any further information about the police officer who was shot in the holster.