A gunman killed four people Wednesday during a shooting inside a Tulsa, Oklahoma hospital complex. It wasn't the only active shooting happening during that time.

An inmate receiving treatment at a hospital in Dayton, Ohio, shot and killed a security guard before shooting himself near the hospital emergency entrance, according to Dayton police.

A person was shot outside a Walmart in Pittston, Pennsylvania, during what police called an "attempted homicide."

A student was shot Wednesday afternoon outside a high school in Valley Glen, California, authorities confirmed.

Although the shootings were not considered mass shootings, in which four or more people are shot, all of the shooting occurred at the same time.

There have been 20 mass shootings in America since the Uvalde, Texas, mass shooting that left 22 people dead at Robb Elementary School on May 24, according to Gunviolencearchive.com.