The shooter wounded several TSA officers, killing one of them, Los Angeles Mayor Eric Garcetti said. The officer, identified as Gerardo I. Hernandez, 39, is the first TSA officer killed in the line of duty.
Video from the LAX cam shows the chaos moments after the shooting: crowds of passengers running from the airport. Inside, some people hid in bathroom stalls while others were stranded on the tarmac.
The airport was evacuated, and flights temporarily grounded.
Several celebrities, including actor James Franco, updated images to social media. Franco's flight was delayed.
Police eventually cornered Ciancia. A photo appears to show the assault weapon. What sparked the rampage is still unclear.
Reports indicate Ciancia was carrying a note with anti-government sentiments and saying that he expected to die in a shootout.
"There were more than 100 more rounds," the mayor said.