Police officers in Pasadena, California were swarmed by 40,000 killer bees at a Hampton Inn while responding to a report of a single bee sting-- it was a bee ambush.

Killer Bees, 40,000, Police, SwarmSean Gallup / Getty Images

"I've been with the fire department 18 years now and responded to several bee incidents," explained Lisa Derderian of the Pasadena Fire Department to CNN. "But never to this magnitude. The bees were very aggressive. Somebody could have had an allergic reaction and it could have been serious and or fatal."

Five individuals have since been hospitalized from the incident, three of which are first responders.

A bee expert who was brought to the scene estimated there to be between 30,000 and 40,000 Africanized bees.

The first firefighter to head in was stung 17 times.

The hive has since been removed and the bees have vacated the area. It was located on the roof of the four-story Hampton Inn and required carbon dioxide and foam extinguishers to be taken down. 

Africanized bees, commonly referred to as killer bees, are a hybrid that was first introduced in 1956, in Brazil, in an attempt to increase honey production; however, 26 swarms escaped quarantine and soon spread throughout North and South America. They've been known to kill humans, horses, and other animals.