Tony Melendez, manager of Lock N Load said all customers' purchases are confidential, but the store never sold a gun to Dorner because he was a California resident.
"He never purchased any firearms in the store," Melendez said.
A California resident would not be able to legally purchase a firearm in Nevada or another state without having the weapon transferred to a federally-licensed gun dealer in California.
Southern California law enforcement officers escalated a manhunt for Dorner on Thursday after he allegedly used a rifle killed one Riverside police officer and wounded another during an early morning ambush attack.
The multi-agency manhunt for Dorner is currently focused on the Bear Valley area.
Dorner is also suspected in the Sunday night killing of Cal State Fullerton assistant women's basketball coach Monica Quan and her fiancee, USC public safety officer Keith Lawrence.
Quan, 28, was the daughter of Randal Quan, a retired Los Angeles police captain who became an attorney. Quan represented Dorner at the LAPD hearing that led to Dorner's firing.
Dorner wrote in his manifesto that he believes he was unjustly terminated for reporting police brutality and is willing to commit "horrendous murders" and "necessary evil" to change the LAPD.
The rambling manifesto also complains that gun laws are too loose and Dorner states he made multiple purchases of suppressors with a trust account he created using Quicken software to avoid a proper background check.
Although Dorner does not specifically say what he purchased from Lock N Load, he singled out the Las Vegas gun retailer for verbal attack.
"Lock N Load just wanted money so they allow you to purchase class III (sic) weapons with just a notarized trust, miltary ID. Shame on you Lock N Load," Dorner wrote.
A Class III firearms license allows a dealer to sell silencers, machine guns and short-barrelled rifles or shotguns regulated by the National Firearms Act.
Dorner's manifesto also attacks several police officers, National Rifle Association leader Wayne LaPierre, the Westboro Baptist Church and people who have doubted President Barack Obama's status as a natural born citizen.
"Nobody likes to hear the name of their business listed in this manner, but this is a guy whose pain goes deeper," Melendez said.
Melendez recalled that Dorner visited the gun store about once every other month, or about four times since he has been employed at the store.
"This was a guy who appeared to us as your average gun enthusiast," Melendez said. "Very personable. Very kind. Very friendly."
Irvine Police Lt. Julia Ingen said the department is not identifying what kind of weapon Dorner is suspected of using to kill Quan and Lawrence to avoid jeopardizing their investigation.
Other law enforcement officials involved in the Bear Valley search have also refrained from saying which guns Dorner is suspected of using.
Los Angeles Police Chief Charlie Beck, however, said Thursday that Dorner is believed to in possession of multiple weapons, including assault rifles.
The Los Angeles News Group contributed to this report.