Officer Jimenez was on routine mail run when he rushed to Mercy Hospital

Chicago Police Officer Samuel Jimenez was in a squad car on a mundane assignment to deliver mail on Monday afternoon when he saw that fellow cops were speeding toward Mercy Hospital.

Jimenez, an officer assigned to the Wentworth District on the South Side, decided to back up his fellow officers.

He entered the hospital at 2525 S. Michigan and was shot by Juan Lopez, who police say killed his ex-girlfriend in the parking lot minutes earlier.

In the end, Lopez, 32, lay dead in a hallway of Mercy Hospital. The whole incident lasted about 20 minutes.

Police say Lopez killed three people: his former fiancee Dr. Tamara O’Neal, 38, who was an emergency room doctor at the hospital; Dayna Less, 24, a pharmacy resident; and the 28-year-old police officer who was on the job less than two years.

In three decades, there hasn’t been a deadlier shooting spree in which a Chicago police officer was among those killed.

But the carnage could have been even worse, police said.

Police recovered more than 30 spent bullet cartridges from the parking lot and inside the hospital — all from Lopez’s 9mm Glock 17 handgun. Amazingly, though, Chicago police officers fired only four or five rounds during the entire ordeal, police said Wednesday.

A member of the police department’s Special Operations Response Team was the officer who shot Lopez, police said.

The 12-year veteran fired his M4 carbine at Lopez inside the hospital and struck the gunman in the abdomen. Lopez then shot himself in the head, police said.

“We took the power away from the shooter to kill anyone else,” said Tom Ahern, a spokesman for the police department. “We also took his power for him to be in control throughout this entire killing spree by shooting him.”

Anthony Guglielmi, the chief police spokesman, added: “The casualty number could have been much, much higher.”

The special operations team operates three vehicles that continually patrol the streets across the city, Guglielmi said. The officers are equipped with assault rifles, handguns and other weapons.

The idea is to have highly trained officers who are always positioned to be close to a potential situation involving a gunman — just like what happened Monday afternoon, Guglielmi said.

The fact that the officers fired only a handful of shots at Lopez “speaks to their training, their precision,” he said.

On Wednesday, Guglielmi also provided more details about how the situation unfolded at the hospital.

Police had received 911 calls around 3:17 p.m. saying Lopez was assaulting O’Neal and might kill her. Lopez had asked O’Neal to return her engagement ring. When she said she didn’t have it, he shot her six times, police say.

Officers in the squad car for Beat 163 in the Central District were the first ones to arrive on the scene. Lopez fired repeatedly at the car, but the officers were not wounded.

After O’Neal was wounded, officers positioned their squad cars around her body to try to prevent Lopez from shooting her again.

One of the officers began administering first aid to O’Neal.

Lopez opened fire on that officer, hitting his holster and his handgun but not wounding him. One of the bullets lodged in the officer’s gun.

“That’s a heroic measure on their part,” Ahern said of those officers, including the one whose holster was struck.

Lopez then ran into the hospital and shot Less as she stepped off an elevator with another woman.

At some point, Jimenez and his partner entered the hospital to “establish a perimeter,” Guglielmi said.

Lopez fired on Jimenez and fatally wounded him, Guglielmi said. The officer was treated inside the hospital before he was transferred to the University of Chicago Medical Center.

Meanwhile, three officers on the special response team had arrived in their vehicle within two minutes of the original call that shots were fired in the parking lot, Guglielmi said. They confronted Lopez in a hallway in the hospital. He was peeking around a corner and shooting at them.

Sources said Lopez was armed with a handgun that he purchased at Shore Galleries in Lincolnwood in 2012. He had bought three other guns over a five-year period, officials said.

Lopez got his guns legally, authorities say. He held a state Firearm Owners Identification card and a state concealed-carry permit.

Lopez didn’t have any convictions or other issues in his background that would have prohibited him from owning a firearm, authorities say.

But he did have legal issues that, in hindsight, have raised serious red flags about his state of mind. In 2014, for example, his then-wife had obtained an emergency order of protection against him. She complained that he once pointed a gun at a real-estate agent and threatened to show up at her workplace and “cause a scene.”

FOID cardholders are prohibited from having existing protection orders against them, but that emergency order lasted only 16 days — not enough time to jeopardize Lopez’s FOID status, officials say.

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