ANCHORAGE, Alaska - A helicopter pilot was killed in a crash last year while trying to free a bull on a cattle ranch that had become ensnared in plastic wrapping material, according to a National Transportation Safety Board investigation.

Lonnie Kennedy, 48, was killed June 19, 2010, on the ranch on Umnak Island in the Aleutian Islands in southwest Alaska.

The Anchorage Daily News reported Wednesday that the NTSB report says the helicopter crash occurred when a landing gear skid hooked the plastic-wrapped animal and briefly lifted it from the ground, perhaps several feet.

The problems began as Kennedy and two ranch hands at the Bering Pacific Ltd. cattle ranch attempted to remove plastic sheeting from the uncooperative bull, NTSB investigator Larry Lewis wrote in his report.

The bull was tangled in plastic sheeting, and Kennedy, piloting the chopper, tried to herd the animal toward the ranch hands so they could cut off the plastic, Lewis said. The cattle range is unfenced.

After the first attempts to herd the bull didn't work, Kennedy landed on a trailing piece of plastic so the ranch hands could try to tackle the bull, the report says. Then Kennedy appeared to try to knock the bull down with the helicopter, the witness told Lewis.

"Herding animals with helicopters is a fairly common practice," Lewis said. "Now, as far as making physical contact with the animals, that's a different story."

The witness told Lewis that the pilot then hooked the chopper's right skid under the plastic and tried to lift up the bull. The plastic broke, the report says. The helicopter skid hooked the plastic a second time, the report says, and this time the helicopter lifted the bull off the ground. But the added weight caused the chopper to pitch forward and to the right, the report says.

The helicopter slammed into the ground, damaging the fuselage and causing Kennedy's fatal head injuries, the investigator said. The bull also died, Lewis said.

An autopsy of the body in Anchorage showed no evidence of alcohol or drugs in Kennedy's system, according to Lewis' report.