STUART, Fla. -

Police say an 11-year-old boy died when the boat he lived on with his parents caught fire in the waters off Stuart. Both of his parents were airlifted to Jackson Memorial Hospital to be treated for smoke inhalation.

Police spokesman Brian Bossio said Charlie Birely had autism and his parents tried to rescue him as the boat was engulfed in flames Sunday morning on the St. Lucie River.

Bossio says Birely and Lake were not able to save Charlie and made their way into a "small dinghy-type vessel" where they were rescued. Officers were unable to board the sailboat because of the fire's extreme heat.

Bossio says the state medical examiner's office was going over the wreckage Monday. City police are investigating the fire with several other agencies, but say a propane tank exploded after the initial fire broke out.