A Chicago police officer and two hospital employees, including an emergency room doctor, were killed Monday afternoon when a gunman opened fire at Mercy Hospital & Medical Center on the city’s South Side, authorities said. >> Read more trending news The gunman was found dead after officers responded to the scene just before 3:30 p.m. CST. It wasn’t immediately clear whether he killed himself or was fatally shot by police. The victims were identified as Officer Samuel Jimenez, Dr. Tamara E. O’Neal and Dayna Less, who worked as a pharmaceutical assistant at the hospital, officials said Monday night. >> PHOTOS: Chicago Mercy Hospital shooting leaves 4 dead, including officer, gunman “This tears at the soul of our city,” Mayor Rahm Emanuel, who was visibly shaken, said at a press conference. “It’s the face and consequence of evil.” The shooting started in a parking lot outside the hospital after a “domestic dispute” between the gunman and O’Neal, who had broken off an engagement with the suspect in September, according to Chicago Police Superintendent Eddie Jackson. After shooting O’Neal, the gunman continued his rampage, running into the hospital and randomly shooting others in his path, Jackson said. Update 10:05 p.m. EST Nov. 19: The Chicago police officer killed in the line of duty Monday during a hospital shooting rampage had been with the force less than two years, authorities said. Officer Samuel Jimenez, 28, was a married father of three, who did not have to respond to the deadly shooting at Mercy Hospital, according to Police Superintendent Eddie Jackson, because it was out of his district, but he did and it cost him his life. “He was the real police. He wasn’t in it just for the paycheck,” an officer who worked with him told the Chicago Sun-Times. Update 9:10 p.m. EST Nov. 19: Chicago police have identified the officer who was shot and killed at Mercy Hospital Monday afternoon while responding to an active gunman. “It's with profound sadness that we share the death of PO Samuel Jimenez from tonight's senseless active shooter incident,” police spokesman Anthony Guglielmi said in a social media post. Police also confirmed during a press conference Monday night that a doctor at Mercy Hospital and another employee were fatally shot. Update 8:45 p.m. EST Nov. 19: The Chicago police officer critically injured in a shooting at Mercy Hospital Monday afternoon has died, according to The Associated Press. The officer was shot while responding to an active gunman at the hospital. Update 8:05 p.m. EST Nov. 19: A doctor reporting to work Monday at Chicago’s Mercy Hospital was reportedly the first person shot in the parking lot before the gunman made his way inside. She has been identified by WLS-TV as Dr. Tamara E. O’Neal, a doctor of emergency medicine at Mercy, who was shot by her former fiance before he continued shooting inside the hospital. Update 7:55 p.m. EST Nov. 19: While one police officer was critically injured in a shooting Monday afternoon at Mercy Hospital, another is crediting his gun and holster for saving his life. The CPD officer showed TV station WLS his holster where a bullet smashed through the container, but did not penetrate, and his gun with a bullet embedded in it. Update 7:30 p.m. EST Nov. 19: Witness are recounting horrifying descriptions of the shooting Monday afternoon at Mercy Hospital in Chicago. James Gray told the Chicago Tribune that he was coming out of a clinic area at the hospital when he saw the gunman, who was dressed in a black hat and coat, walking and talking with a woman outside the hospital before shooting her three times in the chest. Gray then said the man stood over the woman and shot her three more times after she was on the ground. He told the Tribune that a police car came upon the scene and the gunman started shooting at officers. “It was chaos,” said Gray. “It was just mass chaos.” The gunman went inside the hospital and Gray said it looked like he was just randomly shooting at people. “And then I ran into the X-ray department and locked the door behind us,” he told the newspaper. “I thought it was unbelievable,” said Gray. “It’s like a movie scene. Nothing like that ever happened to me before.” Update 7:00 p.m. EST Nov. 19: Witnesses to the shooting at Mercy Hospital in Chicago describe a terrifying incident as a well-armed gunman opened fire, striking several people outside the hospital, including a police officer, before making his way inside the facility. “It scared everybody,” Steve White, a patient at the hospital, told WBBM-TV. White, who was being treated for dehydration, described a chaotic scene as people inside the hospital heard shots coming from the parking lot, before the gunman entered the facility through the main entrance, WBBM reported. “I have never seen nothing like this in my life,” White said. “This is crazy” Two of the victims were women, according to WLS-TV. One was taken to Northwestern Memorial Hospital in extremely critical condition. The other was taken to the University of Chicago Hospital, also in extremely critical condition, the TV station reported. One of the women was a doctor at Mercy Hospital reporting to work when she was shot in the parking lot by her former fiancé. Update 6:30 p.m. EST Nov. 19: One of the shooting victims was a doctor reporting for her shift at work, according to WLS-TV, and was shot by her former fiance. Update 6:07 p.m. EST Nov. 19: The suspected gunman in the shooting at Chicago’s Mercy Hospital was killed and four people were critically injured, according to the Associated Press, after the unidentified shooter opened fire Monday afternoon. Witness James Gray told Chicago television station WLS-TV that he saw multiple people shot. 'It looked like he was turning and shooting people at random,” Gray said. Update 6:05 p.m. EST Nov. 19: Witnesses described a terrifying ordeal after at least one gunman opened fire at Chicago’s Mercy Hospital. Hospital employee Erix Horton told the Chicago Tribune that he was outside smoking a cigarette when he heard the shooting unfold. “I was checking out, getting ready to leave,” Horton said. “One of the nurses ran back here and it was like she was about to collapse and said (a staff member had) been shot. And she’s like, ‘Call the police. We have an active shooter.’ And that¹s when everybody took cover. They got on the PA, letting everybody know.' Horton told the Tribune he took cover in a break room with others until police rescued them. He said an emergency crew had just brought in a patient and had to take cover, too. He said he heard someone firing eight to nine shots in the hallway outside the break room. 'We had to duck,” he said. Employees at the hospital were eventually loaded on to buses and taken to safety. Update 5:45 p.m. EST Nov. 19: At least two people were killed in a shooting at Chicago’s Mercy Hospital Monday afternoon, according to WLS-TV. At least one witness told reporters there was more than one shooter at the hospital and that shots were fired into a lab at the facility. Update: 5:35 p.m. EST Nov. 19: Chicago police confirmed at least one shooter was shot. People at the hospital when the shooting unfolded described hearing multiple shots and hiding inside hospital rooms. Update 5:20 p.m. EST Nov. 19: The Chicago police officer shot during the shooting at Mercy Hospital is in critical condition, according to WLS-TV. It’s still unclear exactly how many other people were injured or killed. Original report: Authorities contained the shooter, according to a number of media outlets, and are now searching the hospital. There’s no report, yet, on how many victims may be involved. Roads around the medical center have been shutdown as the investigation continues. Emergency crews were called to the scene just before 3:30 p.m. Monday on “reports of multiple victims,” according to the Chicago Tribune. Hospital employees were evacuated in buses, WBBM reported. Check back for more on this developing story.