CHICAGO (CBS)–A day after the Mercy Hospital shooting that destroyed so many families, new details are emerging about 32-year-old gunman Juan Lopez.

Lopez, who killed three people Monday before he was fatally shot, was fired from the Chicago Fire Department Academy for harassing colleagues, according to Chicago Police Superintendent Eddie Johnson, who spoke at a police press conference Tuesday at Little Company of Mary Hospital in Evergreen Park. A police officer was treated and stabilized there after being shot Tuesday morning in a separate incident in the Gresham neighborhood.

juan lopez New Details On Juan Lopez, Mercy Hospital Shooting Gunman

Juan Lopez, 32, shot and killed three people at Mercy Hospital on Nov. 19, 2018. Chicago police said Lopez also was killed. (Source: Facebook)

Lopez was also a student at DePaul University, where he earned a bachelor’s degree in public service in 2013. He was currently enrolled at DePaul seeking his master’s degree in the same program.

CBS 2 investigator Pam Zekman has also learned that Lopez used to work in security for local hospitals.

Lopez’s ex-fiance Tamara O’Neal–who Lopez fatally shot Monday afternoon before killing 24-year-old pharmacy resident Dayna Less and 28-year-old Chicago police officer Samuel Jimenez–apparently met Lopez through work.

“He came over there because they had broken off their engagement and he wanted his engagement ring back, that’s what brought him over there,” Johnson said.

Johnson said records show Lopez had purchased four weapons in the past five years.

Garth Walker, O’Neal’s colleague, remembers meeting Lopez on several occasions.

“The story I remember (is) he was a security guard at either Mercy or Masonic while she was an attending and that’s essentially how they met,” Walker said. “But they loved each other, as much as I could gather.”

Meanwhile, authorities revealed Tuesday that Lopez had a concealed carry permit. Chicago police spokesperson Tom Ahern said the gun used in the shooting, a 9 mm semi-automatic handgun, was purchased legally from a suburban gun shop. Ahern declined to name the store that sold the firearm.

Lopez’s cause of death, released by the Medical Examiner’s Office Tuesday, shows he died of a gunshot wound to abdomen with a self-inflicted gunshot wound to the head as a contributing factor.