An Orange County Sheriff's Department spokesman told ABC News that the agency was contacted by the Chicago Police Department after a sheriff's lieutenant, speaking at a Monday news conference, described the pilot as a former officer.
It was not immediately clear why the man, identified as 75-year-old Antonio Pastini, was in possession of the fake credentials. According to authorities, his other identification details and his Federal Aviation Administration pilot's license are still believed to be authentic.
Dashcam video: Plane bursts into flames in midair before Yorba Linda crash
As of Tuesday morning, the coroner was still in the process of identifying the four badly burned victims -- two men and two women -- who were killed in a home that was struck by the plane's debris. Their conditions require additional measures -- including DNA -- to reach official identifications.
A close friend of the deceased said the family had gathered for their annual Super Bowl party when the deadly incident occurred.
The small plane ascended to about 7,800 feet before it crashed about 10 minutes after taking off from the Fullerton Municipal Airport, National Transportation Safety Board investigator Maja Smith said. Its wrecked fuselage ended up in a residential backyard.
Shawn Winch, who lives near the two-story home that erupted in an inferno, said the plummeting aircraft "sounded like a missile coming at my house."
"I got over there and the house was just engulfed in flames," he said. "Stuff was blowing up in the garage and everything else. It was horrible."