Police in Tinicum Township, Pa., west of the Delaware River, were called about 6:30 a.m. after neighbors reported hearing a loud explosion. Investigators said the helicopter was so badly burned they couldn't immediately ascertain its registration number.
Small aircraft such as helicopters don't require flight paths or passenger manifests making it unclear initially where Brigham -- a great-grandson of former President Herbert Hoover -- was headed or whether anyone else was onboard.
The National Transportation Safety Board will investigate the crash, officials said.
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