Police stormed Terminal 4 at the airport Friday night after receiving a call -- "probably a prank," said airport police chief Patrick Gannon -- that a man with a gun was in the building, CNN reported Saturday.
Officers came to the terminal with guns drawn and shouted at people to get on the ground, but found no shooter or any evidence there had been one.
"We did not find anybody there with a gun. In an overabundance of caution, we evacuated terminal 4," Gannon said. "We had great cooperation with our passengers."
Complicating matters, about the same time, some travelers in Terminal 5 evacuated themselves after a woman suffering a medical emergency behind the wheel lost control of her sport-utility vehicle and crashed near an exit.
Gannon said the driver was in good condition at a hospital.
The incidents come three weeks after a man shot and killed a Transportation Security Agency officer Gerardo Hernandez and wounded several others at LAX.
CNN said an autopsy showed Hernandez was shot 12 times by the suspect, Paul Ciancia.
Police said they shot Ciancia multiple times during the exchange but he's since been released from the hospital and is in U.S. marshals' custody.
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