CHICAGO — A police officer, a doctor and a pharmacy resident died on Monday after gunfire broke out in the parking lot of a hospital and then moved inside.

The chaos, the authorities said, began as an argument between the gunman and the doctor, Dr. Tamara O’Neal, with whom he had a relationship. Patients and hospital workers fled the emergency room or hid in rooms as the situation escalated.

By Tuesday, bunting was hung at Chicago Police Headquarters in memory of Officer Samuel Jimenez. And colleagues were mourning Dayna Less, the pharmacy resident, who recently joined the hospital staff and who was not involved in the initial dispute.

The episode raised hard questions about the links between domestic disputes and shootings, as well as other concerns around gun violence. Here’s a look at some of the issues:

Guns make domestic disputes deadlier

Domestic violence has long been known as a major risk factor for homicides of women. Researchers have found that women are killed by intimate partners, such as spouses or boyfriends, more often than any other kind of perpetrator. And the presence of a gun in a domestic violence situation makes it five times more likely that a woman will be killed.