(NewsNation) — While most active shooter incidents are random, ones that happen at health care facilities are often personal and targeted.

According to the most recent data from the FBI in 2019, two out of 28 total active shooter incidents were at health care facilities. In non-health care facilities, fewer than 25% of the victims have had a relationship with the shooter. But in hospital settings, more than 50% of the time, the victim and the shooter have known each other.

Those shootings in hospitals are often targeted against a doctor, nurse, colleague or someone the shooter knows.

In the case of a Wednesday shooting at a hospital in Tulsa, Oklahoma, the gunman blamed his surgeon for continuing back pain after a recent surgery. In a letter police found on the gunman, who died of self-inflicted gunshot wounds, he threatened to kill the surgeon, Dr. Preston Phillips, and anyone who got in his way.

The shooting in Tulsa was not the only shooting at a health care facility Wednesday. A security guard was shot and killed by a patient in Dayton, Ohio, earlier that day. NewsNation local affiliate WDTN reported that an inmate was receiving treatment in the emergency room at Miami Valley Hospital when he stole a pistol off an armed security guard charged with watching him.

So far in 2022, there have been more than 200 mass shootings reported. Since last Tuesday, when a gunman opened fire in a Uvalde, Texas, elementary school, there have been 20.

A mass shooting is defined as a single incident where four or more people die, not including the shooter.