Firefighters transported two patients from the scene in moderate condition. The injuries are not believed to be life-threatening.
The crash was reported just before 2 p.m. to the east of Fullerton Municipal Airport, in the area of N. Gilbert Street and Artesia Avenue.
The wreckage of the plane was upright at the scene and partially wrapped around a tree next to a commercial building. While the cockpit appeared seriously damaged, it wasn't clear if any of that was caused by the crash itself or by firefighters cutting open the cockpit to extricate the occupants.
Dramatic video captured the moment the plane crash-landed on the street and slammed into the tree.
In the video, the plane's wing clips a light pole, shearing off the top and sending the plane careening off the road. It appeared the plane would have crashed head-on into the tree, but the other wing clips a fire hydrant and turned the plane slightly at the last moment.
Moments after the crash, a truck stopped and two men got out to help, but the two people in the plane had to be cut out of the wreckage. Cellphone video shows the two victims being loaded onto stretchers and taken to local hospitals.
Firefighters say the pilot radioed in an issue with the plane while trying to return to Fullerton airport. The crash site was about a half-mile short of the runway.
The plane went down just four minutes after takeoff.
FAA records indicate the aircraft is a single-engine Mooney M20F built in 1969.
The cause of the crash remains under investigation.