According to a Los Angeles Times article:
Two plainclothes security officers — one male, one female — escorting a prisoner in handcuffs provided documents to officials at a checkpoint in Terminal 3 about 8 a.m., saying they had the authority to escort him to Hawaii for a court hearing, law enforcement officials said.A report on SFGate.com says that the woman told TSA personnel at an LAX screening area that she was carrying a firearm, and that she had documents to show that she was authorized to carry the weapon.
Airport police ran a check and determined that the pair were not police officers, nor did the woman have a permit to carry a gun. The two were arrested for impersonating police officers, and the woman also was charged with carrying a concealed weapon.
A report about the arrest on NBC4.tv in Los Angeles mentioned that the pair were bounty hunters.