Reuters
Only the pilot was aboard the plane when it crashed. It is not confirmed whether Horner, 61 years-old and a keen aviator, was the pilot
Fire officials say they found the wrecked plane about 2 miles west of Highway 33 in Southern California. Officials discovered the tail section of Horner's two-seater S312 Tucano MK1 single engine turoprop plane, according to Mashable.
One of Horner's attorneys Jay Cooper told The Daily Mail that the plane was one of several owned by Horner. He also noted that "if [Horner] wasn't in it, he would have called."
In an interview with KNBC-LA, Cooper said, "We haven't heard from James ... We don't know where he was headed...He flies a lot and is an experienced pilot."
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His agency has not commented on the crash and his lawyer told Mashable no one has heard from Horner since the crash was reported around 9.30am local time.
Horner is best known for his work on James Cameron's "Titanic," for which he won Oscars for best original dramatic score and best original song for "My Heart Will Go On." Horner also composed the scores for "Braveheart," "Glory," "Avatar," "Legends of the Fall," and "A Beautiful Mind."
TMZ captured video of the crash scene, which you can see below.