PORT ALLEN - An early report from federal investigators offered the first insight into what happened in the moments leading up to an out-of-state plane crash that killed a mom and her two children from the capital area. 

Sandra Kirby and her kids, 17-year-old Ian and 13-year-old Amanda, died July 17 while on a sightseeing flight in Boulder Colorado. The plane's pilot also died in the crash.

According to the preliminary report from the National Transportation Safety Board, witnesses said the right wing of the aircraft "rose abruptly" before the nose of the plane pitched down. The aircraft then reportedly "corkscrewed out of view" before hitting the ground.

The full findings of the investigation are pending the NTSB's final report. 

Port Allen High, where Ian attended school and played band, honored the family during a memorial service last week.