Click in the Eyewitness News story window above to watch Sid Garcia's report from San Dimas.
Thomas Angster and his sons were at their motor home when they saw the plane coming down right at them.
It was around 8:45 p.m. Tuesday when they saw and heard the plane in trouble. It was heading straight for the East Shore RV Park in Bonelli Regional County Park.
"Well we heard it cutting out as it came across the far section of the lake over there. He just started turning really hard to the left. He then came right over the top of the motor home. It was something," said Thomas Angster, an eyewitness.
"It was scary and they were screaming for help. He ran back here and got the fire extinguisher and then ran into the fire," said Landon Angster, an eyewitness.
According to the National Transportation Safety Board, the two men onboard the plane, both commercial pilots, took the plane out for a demonstration flight. The twin-engine Piper PA-23 took off from nearby Brackett Field Airport in La Verne.
The two pilots were airlifted to County USC Medical Center in stable condition. One of the pilots reportedly suffered a broken leg and the other a broken arm.
"The main fuselage of the aircraft, the passenger compartment, pretty much stayed in tact, which adds to the survivability," said Patrick Jones, NTSB.
On July 4, 2002, a small plane crashed in Bonelli Park on the beach killing four people. Two adults onboard the plane and two children on the ground died in the accident.
"You feel safe but you always wonder, what if. We finally saw it happen and I guarantee that everybody around here will have a pretty good fire extinguisher by this weekend," said Thomas Angster.
"All of sudden the motor popped, bong, and all of a sudden there was no motor, and everything got dark, and the plane started descending towards the lake here. At that time I started running that way. He banked off to the left, where he ended up crashing. There were two people in there," said Sammy Rodela, who witnessed the crash.
"I watched it barely clear those trees, and I saw it impact into that hill. And let me tell you, I'll never forget it man. We all ran over there. And I came back, got my fire extinguisher, and that's when I heard the guy started screaming, and one of them was out," said Thomas Angster.
Firefighters quickly put out a small fire caused by the crash.
Federal investigators are still working to determine what caused the plane to go down.