The Bureau of Land Management said the ranger was patrolling the course in the Johnson Valley off-highway vehicle area on Aug. 14 when a spectator flagged him down and reported the truck had slammed into the crowd and overturned.
"The ranger immediately responded, and once at the scene, quickly assessed the situation, and called for emergency support," said Jan Bedrosian, BLM deputy state director of external affairs, said in a statement.
The BLM, which issued permits for the California 200 race, has maintained that the event's organizer was responsible for spectator safety.
The tragedy has raised questions about the agency's oversight of such events.
"It's clear that the law enforcement presence was inadequate the night those people were tragically killed," said Daniel Patterson, Southwest director of Public Employees for Environmental Responsibility. "Those deaths were preventable. Better decisions from the BLM could have helped keep those people alive."
The BLM's field office in Barstow, which oversees the Johnson Valley, has 10 rangers on staff to patrol approximately 300,000 acres of land that are open to off-road vehicles, according to documents filed by the BLM.
In an effort to step up enforcement following the crash, the BLM had eight employees, including three rangers, staff a motorcycle race in the same area last weekend.