Five people were killed when two airplanes collided into one another near an airport in Southern California. The crash occurred around 11 a.m. Sunday, about 2 miles northeast of Brown Field Municipal Airport in San Diego County, said Federal Aviation Administration spokesman Ian Gregor, according to Yahoo! News.

The planes involved in the crash were a twin engine Sabreliner and a single-engine Cessna 172, reported NBC San Diego. The Sabreliner, which had four people onboard, was registered to BAE Systems and was in the middle of a mission training flight, revealed the National Transportation Safety Board in a statement.

"BAE Systems was alerted this afternoon that a small aircraft carrying its employees collided with another," said the company in a statement to NBC San Diego, adding that its "employees and their families are our first priority and we are prepared to offer all our support."

NTSB investigator Andew Swick noted that the pilot of the Cessna, who also died in the crash, was on a cross-country trip.

The two aircrafts landed at least a mile apart from each other, reported Fox News. The Sabreliner fell on a grassy slope, and the Cessna fell within the bounds of the San Diego National Wildlife Refuge.

Initially, investigators confirmed four deaths as a result of the crash. However, later Sunday evening, NTSB officials updated the death toll to include a fifth casualty.

Upon impact with the ground, both aircrafts caught on fire and broke apart. Two small grass fires were ignited by crash debris and were quickly extinguished. However, fire officials noted about two acres burned near where the Cessna crashed.

"It appears that it was a very violent crash as you can tell by both aircrafts that are in multiple pieces," said Cal Fire Division Chief Nick Schuler.

One firefighter was taken to the hospital after he suffered a minor heat-related exhaustion injury.

The details of the crash are under investigation by the FAA and NTSB.