Minutes before a gunman opened fire in a Los Angeles International Airport terminal last fall, killing a security screener and wounding three others, the two armed officers assigned to the area left for breaks without informing dispatch as required.

Two law enforcement officials told The Associated Press that Los Angeles Airport Police Department officers were outside Terminal 3 when authorities say Paul Ciancia opened fire with an assault rifle in an attack targeting Transportation Security Administration officers.

The officials, who were briefed on the shooting, requested anonymity to speak publicly about an ongoing investigation.

Department policy requires officers to notify dispatch before going on break and leaving their patrol area in order to ensure supervisors are aware of their absence and, if necessary, a relief unit can be brought in.