Tragedy struck the city of Chicago Monday (Nov. 19) as a shooter attacked citizens at Mercy Hospital. ABC 7 Chicago reports four people were killed in the shooting. Of that four were Samuel Jimenez, a Chicago police officer, Dr. Tamara O’Neal, an emergency room doctor and Dayna Less, a pharmacy resident. The shooter was the fourth killed in the incident.

The gunman was identified as 32-year-old Juan Lopez. Lopez began shooting outside the hospital as a result of a domestic disagreement between Lopez and Dr. O’Neal. Lopez shot O’Neal in the parking lot before entering the hospital and continued to shoot, hospital officials exchanged gunfire with Lopez inside the hospital.

Reports from relatives state Dr. O’Neal was scheduled to marry Lopez this past October but called off the wedding.

Additional details state the shooter shot the woman multiple times in the parking lot before entering the hospital. Lopez was fatally shot in the hospital, it is unclear at the time if it was by a himself or police.

Officer Jimenez was saluted at the scene while he was carried away by ambulance.

“Today the Fraternal Order of Police lost a valued brother, a courageous police officer who got up this morning went to work and wanted to protect the city of Chicago,” said Kevin Graham, president of the Fraternal Order of Police. “He did just that, but he did so with his life.”