The killing of Dr. Tamara O’Neal, 38, shows once again that domestic violence has no boundaries.

It lurks in the posh communities, sleepy suburban villages, working-class enclaves and poverty-stricken neighborhoods.

On Monday afternoon, it showed up at Mercy Hospital and Medical Center, in the heart of Chicago’s Bronzeville neighborhood.

And within minutes, a gunman with a license to carry had killed his former fiancée, a medical doctor, Chicago Police Officer Samuel Jimenez, 28, and Dayna Less, 25, a first-year pharmacy resident.

The gunman, identified as Juan Lopez, was found dead of a gunshot wound.

There is no way to know when an abusive relationship will turn deadly, though experts say the most dangerous time for a woman is when she is trying to leave the relationship. According to a friend that witnessed the altercation between O’Neal and Lopez, he wanted the engagement ring back.

Craig Elliott’s 9-year-old son was among the last patients that O’Neal treated.

Craig Elliott's young son was treated by Dr. Tamara O'Neal just hours before she was gunned down at Mercy Hospital.

Craig Elliott’s young son was treated by Dr. Tamara O’Neal just hours before she was gunned down at Mercy Hospital.

Elliott, 42, lives walking distance from Mercy Hospital. He met his son and the boy’s mother at the hospital emergency room that morning and left the hospital around 12:30 p.m.

“My son had a bit of a cold and a little asthma bothering him. Dr. O’Neal came in and she made him comfortable. She was wonderful. She joked that he was almost her height,” Elliott said.

“She was great, and honestly, to see a young sister doctor — it put a smile on my face. I actually noticed that she had a ring on her left hand,” he said.

Elliott felt a sudden rush of pride at the sight of O’Neal since there are so few black female doctors in the U.S.

According to a recent survey, about 6 percent of physicians and surgeons are black.

“Later that day, I posted a couple of pictures on social media of my son getting treatment, basically saying it was a long day.

“My phone started blowing up. I was thinking it was Facebook and Instagram posts for the little guy to get well, “ Elliott said.

“I live in the South Loop and I heard a parade of police sirens, but I hear sirens all the time. Then my son’s mom called and said, ‘turn on the TV.’ It was surreal. I thought, we just left there,” he said.

“I just saw this woman. She was pleasant. She was happy. She was taking care of the most valuable possession I had on the planet. With [my son] not feeling well and with him being sort of miserable and lethargic, she just added a little more light to the room,” Elliott said.

In an interview with the Sun-Times, O’Neal’s father said his daughter had broken off her engagement to Lopez.

“She broke it off a few months back and he wouldn’t let it go … He couldn’t let go and he took her away from us,” Tom O’Neal said.

In 2014, almost 65,800 intimate violence incidents were reported to Illinois law enforcement, according to the National Coalition Against Domestic Violence.

“The presence of a gun in the home during a domestic violence incident increases the risk of homicide by at least 500 percent. And 72 percent of all murder-suicides involve an intimate partner,” the advocacy group found.

Apparently Lopez had a permit to possess a concealed firearm even though he had a documented history of domestic violence.

Craig Elliott posted a remembrance of Dr. Tamara O’Neal on Facebook.

Elliott, 42, an entrepreneur, business owner and DJ at several popular clubs was impressed with how O’Neal handled his son’s emergency-room visit.

“I know a lot of people in the city. Young, black professionals and so it is very rare that I run across people like that and I don’t know them,” he said.

O’Neal, described as a devoted Christian, was raised in the LaPorte, Ind. Her father said on Sundays, she drove 60 miles to attend church with her family and to direct the church’s choir.

Elliott, the son of a retired Chicago Police officer, was horrified when he found out O’Neal was murdered.

“Rest well, and thank you for taking care of my child,” he said in one of his social-media posts.

That horror was compounded by the killings of Jimenez and Less.

“Whenever I hear of any officers getting killed in the line of duty, I’m always shaken. I grew up not knowing if [my father] was coming home,” he said. “This is again another lesson, another unfortunate situation on gun control in this city.”

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