BRADENTON, Fla. (AP) _ Officials have not been able to determine why a man committed suicide by hurling himself into a landfill incinerator.

James Burnett and a friend had been smoking marijuana and sipping cough syrup in their truck parked near the landfill Thursday afternoon when Burnett walked over to the incinerator and climbed in, witnesses said.

''It wasn't a matter of tripping,'' said Manatee County sheriff's Detective Ned Foy. ''He climbed a ladder and threw himself in.''

Sheriff's spokesman Dave Bristow said Burnett, 30, a gardener who often hauled trees and brush to the incinerator, ''made remarks to his friend ... that made it plain he wanted to die.''

Burnett's friend Greg Mayers told investigators Burnett was depressed.

Dr. John Wilson, with the county medical examiner's office, said soot in Burnett's lungs showed he was alive for several seconds in the 1,250-degree heat.