COLLINSVILLE, Oklahoma - We now know the identity of the two men killed Sunday, when their small plane crashed into a Collinsville home.

Both victims were from Kansas.

No one on the ground was hurt, even though the crash happened almost downtown.

Witnesses said the plane came down at a sharp angle, and in the small yard where it crashed, only one tall tree had broken limbs. The wreckage burned on impact, and pieces of the plane were thrown into the surrounding neighborhood and street.

Two men died in the crash: 71-year-old Ron Marshall was the pilot and 40-year-old Chris Gruber was his passenger.

Monday, investigators with the Federal Aviation Administration and the National transportation safety board started the investigation.

They report no unusual radio communication from the pilot, who had filed an instrument flight plan bound for Manhattan, Kansas.

"Really, what we've got is an impact crater, a post crash fire, and a lot of scattered small parts. That's kind of an indication that when the aircraft hit the ground, it was really out of control, and at high speed, so that's a clue of what we'll be looking at when we look at the airplane," said NTSB Air Safety Investigator Craig Hatch.

The NTSB investigator said one piece of the plane was found almost a mile away, and at least one witness described pieces coming off of the plane.

"We saw it in the air when it popped--something, a couple of things it looked like, fell off, and the wings looked really strange, like they folded in, and it nosed dived, straight into the house," said Stephanie Coldren.

The radar track showed the plane left Tulsa International Airport and flew north just past Collinsville, made a 90-degree turn to the east, and then turned around just before the crash.

The plane was a 1984 Mooney, a four-seat, single-engine plane.

Investigators will look for any clues to the crash in the wreckage, but say they'll start with the human factors.

"We'll start off with the pilot. We'll look at this ratings, his training, his experience in the aircraft," Hatch said.

The pilot was a retired doctor. The passenger worked for the Kansas State University Foundation and was director of development for the university's veterinary medicine college.

They flew into Tulsa Sunday morning, and the crash was on the return flight.