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Two news helicopters fall after colliding in mid-air while covering a police pursuit in central Phoenix, Friday. ((A.J. Alexander/Associated Press))

Two television news helicopters covering a police pursuit collided in mid-air above the city of Phoenix, Ariz., killingall four people aboard.

Both aircraft went down Friday in a public park in central Phoenix and caught fire.

The two choppers were broadcasting live coverage of police cruisers pursuing a truck. Viewers, however, did not witness the crash as cameras aboard the aircraft were pointed at the ground.

But they saw images from one of the helicopters break up and begin to spin before the station abruptly switched to the studio.

Local TV station KNXV said it owns one of the choppers. The other is from KTVK.

KNXV reporter Craig Smith, who was among the dead, was reporting live as police chased a man driving a construction truck. He had fled a traffic stop and was driving erratically, hitting several cars and driving on the sidewalk at times.

Police had blown the truck's tires, and the man eventually parked it, then carjacked another vehicle nearby.

As police closed in, Smith said, "Oh geez!"

After the picture broke up, the station switched to the studio and then briefly showed regular programming, a soap opera, before announcing that the helicopter had crashed.

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

Mary Lewis said she was stuck in traffic with her four grandsons and was watching the helicopters. She turned to talk to the children, then saw a fireball in the air when she looked up again.

"I looked up and I see this 'boom,' and I see one of the helicopters coming down, and I said, 'Oh my God,'" Lewis said. She said she went to the crash site to help, but there was nothing she could do.

"It's nothing there," Lewis said. "Just burned-up stuff."