4 shooting incidents occurred on military bases in the US in 2019

For the second time this week, a military base in the United States faced an active shooter incident. The latest on Friday in Pensacola, Florida, has left four people, including the shooter, dead.

The Friday shooting marked the fourth shooting incident to occur on a military base in the U.S. in 2019, according to news reports.

On New Year's Day, 20-year-old Lance Cpl. Riley Kuznia was killed by another on-duty Marine at the Washington, D.C., Marine Barracks.

Lance Cpl. Andrew M. Johnson was charged with murder in the shooting, which was originally classified as a death investigation rather than homicide, meaning it may have been an accident. A redacted copy of the charge sheets, obtained by Task & Purpose, said Johnson jokingly pointed his pistol at Kuznia's head and pulled the trigger, showing "wanton disregard for human life." Johnson entered a not guilty plea and his case is still pending.

At the Naval Air Station Oceana in Virginia Beach, Virginia, on April 5, 2019, a 25-year-old male Navy sailor was killed by base security after shooting a female sailor in the parking lot. The woman was taken to the hospital for non-life threatening injuries.

Navy police reported the scene as an active shooting incident and it was later deemed a "domestic" incident, according to Navy Times.

A 22-year-old active duty sailor killed two people and injured another on Dec. 4, 2019 at the Pearl Harbor Naval Shipyard near Honolulu, Hawaii, according to authorities.

The shooter opened fire on shipyard personnel with his M4 service rifle and then used his M9 service pistol to shoot and kill himself, an official said.

An active shooter was reported at theNaval Air Station in Pensacola, Florida, on Dec. 6, 2019. Four people, including the suspected shooter, were killed.

In the U.S. between 2000 and 2018, there were 277 active shooter incidents -- "an individual actively engaged in killing or attempting to kill people in a populated area" -- identified by the FBI. In total, 2,430 people were either killed or injured.

Seven of those active shooter incidents were on military property.

ABC News' Elizabeth McLaughlin contributed to this report.