Updated

An internal District of Columbia police report on the response to the Washington Navy Yard shooting says officers were hindered because they couldn't access live surveillance-camera footage of the shooter.

Military contractor Aaron Alexis killed 12 civilian workers before he was fatally shot by police in September 2013.

The report says the contract security guard who was monitoring the surveillance videos locked the door to the control room and didn't contact law enforcement. That prevented police from tracking Alexis' movements in real time or ruling out reports of a second shooter.

The report says Metropolitan Police Department officers were also delayed in getting to the scene because some Navy Yard employees called an internal emergency communications number instead of 911, and officers couldn't get through locked gates when they arrived.