SAN DIEGO -- The pilot and sole occupant of a light plane was killed Tuesday when the aircraft crashed in a field behind a North County primary school and burst into flames.

The twin-engine Beech 95-B55 went down near State Route 76 and North El Camino Real in Oceanside shortly before 11 a.m., according to the Federal Aviation Administration. The airplane had just taken off from nearby Oceanside Municipal Airport, FAA spokesman Ian Gregor said.

Firefighters arrived to find the crumpled aircraft and some surrounding vegetation ablaze. The crews had the flames under control within 20 minutes.

The pilot died at the scene.

Witnesses said the plane was "in obvious distress" just before it went down near San Luis Rey Elementary School, which had no classes in session at the time, Oceanside police Lt. Leonard Mata said.

The pilot -- whose identity remained unconfirmed in the late afternoon -- may have been trying to circle back to the airport to make an emergency landing when the aircraft plunged to the ground about 50 yards south of SR-76, Mata said.

The 42-year-old airplane is registered to a San Clemente man, according to FAA records.

The National Transportation Safety Board will lead the investigation into the cause of the crash, a process that generally takes at least several months, Gregor said.

12-year-old Melanie Martinez said she saw the plane fly over her home.

"We were outside playing and then all of a sudden we heard the big noise. It was over our house and it flew and crashed," she said.

Robert Poff heard and saw the pilot's terrifying moments as the plane departed Oceanside Airport.

"I could hear it," said Poff. "I could hear the sputtering and the pop, pop."

At San Luis Rey Elementary School, right next to the crash site, custodian Ted Chavez said he rushed towards the plane to try and help the pilot. Although school was not in session, Chavez said they train for these types of emergency scenarios because the school is so close to the airport.

"What if this happened... if they're out there with the kids? How would we move them from Point A to Point B? We have those all the time," he said.