Federal investigators hope to determine why two news helicopters covering a police chase on live television collided and crashed to the ground, killing all four people on board.

Both helicopters from local TV stations went down in a grassy park in central Phoenix and caught fire Friday afternoon. No one on the ground was hurt.

TV viewers did not witness the accident because cameras aboard both aircraft were pointed at the ground, but they saw video from one of the helicopters break up and begin to spin before the station abruptly switched to the studio.

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Killed on board the KTVK helicopter were pilot Scott Bowerbank and photographer Jim Cox, the station reported. On board the KNXV aircraft were reporter-pilot Craig Smith and photographer Rick Krolak, that station said.

A Federal Aviation Administration investigator was at the crash scene by late Friday and National Transportation Safety Board investigators were expected to arrive Saturday.

The helicopters were covering the police pursuit of a work truck. Just before the collision, the driver had jumped out of the nearly disabled flatbed pickup and carjacked another truck. The man was later taken into custody by a SWAT team after barricading himself inside a house.

Just before the picture broke up, Smith said, "Oh geez!"

Police identified the suspect as Christopher J. Jones, 23, and said he was booked into jail late Friday night on two counts of vehicle theft, four counts of aggravated assault on a police officer and one count of resisting arrest with other charges expected to be filed later.

Earlier on Friday, Phoenix Police Chief Jack Harris suggested the suspect could "be held responsible for any of the deaths from this tragedy."

The two helicopters came down on the lawn in front of a boarded-up church at the park. Firefighters swarmed to the area as thick black smoke rose from the scene.

Rick Gotchie, an air conditioning contractor, was working nearby when he noticed the helicopters overhead. He said they began circling closer as he continued watching, and one appeared to get too close to the other.

"I kept saying 'Go lower, go lower,' but he didn't," Gotchie said. "It was like a vacuum. They just got sucked into each other, and they both exploded and pieces were flying everywhere."

He said he ran to the crash site, but "no one got out."

FAA spokesman Ian Gregor said the pilots of the five news helicopters and one police chopper over the chase were not talking to air traffic controllers at the time, which is normal.

"Typically air traffic controllers clear helicopters into an area where they can cover a chase like this," Gregor said. "Once they are in the area, the pilots themselves are responsible for keeping themselves separated from other aircraft."

Pilots generally use a dedicated radio frequency to talk to each other and maintain their positions, Gregor said.

"There is a high degree of coordination," Gregor said. "To fly for a TV station you have to have a commercial rating, which means more (flight hours), more training."

Gregor said the FAA has not had major safety problems with news chopper operations.

Keith McCutchen, a past president of the National Broadcast Pilots Association and a news pilot for 11 years in Indianapolis, said pilot awareness is vital while on the scene of a story because of the many distractions that could spell trouble.

"You are watching the scene. You have to bring your attention inside to look at the monitors to see what the audience is seeing so you can converse. But you're also having to direct your attention to the other aircraft flying around you. You have to have your head on a swivel in those kinds of situations."