FORT LAUDERDALE, Fla. (AP) — A pilot told investigators he heard a loud bang before a Florida medical rescue helicopter caught fire in flight last month, leading to a crash that killed a paramedic and a woman on the ground, a federal report released Friday said.

The twin-engine Broward County Fire-Rescue helicopter had just taken off from Pompano Beach Airpark on Aug. 28 when at about 400 feet (122 meters) pilot Daron Roche said he heard the bang, the National Transportation Safety Board’s preliminary report said. Then he saw on his control panel that one engine’s temperature was rising.

He radioed air traffic controllers to tell them that he had an emergency and tried to return to the suburban Fort Lauderdale airport, the report said. The fire warning light had illuminated, so he activated the suppression system but the temperature gauge kept rising, Roche told investigators. Video taken by witnesses on the ground shows flames coming from the engine compartment followed by a trail of smoke.

Roche told investigators he lost control after hearing a second bang, which was when the tail partially separated from the main part of the helicopter.

The aircraft spun out of control and crashed through the roof of an apartment building, killing paramedic Capt. Terryson Jackson and apartment resident Lurean Wheaton. Roche and paramedic Mike Chaguaceda were injured.

The paramedics had been on their way to pick up a seriously injured traffic accident victim.

The helicopter was built in 1999 and its engines were rebuilt seven years ago, the report said. The helicopter was last inspected in May.

The safety board has not yet determined what caused the fire. Its investigations usually take about a year to complete.