Rich Heltebrake has filed a claim to collect the award offered by Mayor Antonio Villaraigosa, the Los Angeles Times reported.
Villaraigosa offered the award to anyone who provided information leading to the arrest or capture of Dorner, a former police officer who authorities said killed four people before eventually killing himself.
Not long after Heltebrake called 911 on Feb. 12 following the carjacking, the Times reported, San Bernardino County sheriff's deputies surrounded a cabin where Dorner was hiding.
In his claim document, Heltebrake said he was driving when Dorner jumped out of a snowbank and pointed a firearm at him.
Dorner ordered him out of his truck and used the vehicle to flee police, the document states.
Dorner drove the truck to his cabin, fatally shot a deputy and then shot himself, authorities said.
The Times said Heltebrake's claim is likely not the only one because other witnesses also called 911.
Los Angeles officials said a decision on the reward will be made after the Dorner investigation is complete.