The backpack later was found hanging on the back of a stall door. It contained a roll of purple duct tape, empty boxes of ammunition, and numerous computer disks and software, according to FBI affidavits.
The documents do not detail the shootings, but a haunting 30-second video provided by the FBI shows some of Alexis’s actions. Dressed in a blue striped polo shirt and dark slacks with what appears to be an ID attached to his belt, Alexis stealthily stalks the hallways and a stairwell with his shotgun in hand, ducking behind walls when someone might spot him.
Valerie Parlave, head of the FBI's field office in Washington, said Wednesday that Washington Navy Yard gunman Aaron Alexis was a mentally disturbed individual.
A picture emerges as eyewitnesses tell what they saw and heard amid the chaos.
Alexis had a checkered four-year career as a Navy reservist and repeated run-ins with military supervisors and the law.
GRAPHIC | Matthew Maasdam offers training to mitigate danger from “active shooter” incidents.
Police received a call reporting an “active shooter” about 8:17 a.m., the FBI said. Officers from Naval District Washington and the Naval Criminal Investigative Service were among the first to confront the gunman, authorities said. At least three D.C. police officers, some armed with only handguns, were inside before heavily armed tactical teams assembled and entered.
The three agents with the NCIS worked in Building 197, where they were assigned to investigate procurement fraud and offer counterintelligence support. Officials said they engaged in two firefights with the gunman in two sections of the sprawling building. Eight additional agents quickly joined them.
Quoting D.C. Police Chief Cathy L. Lanier, Parlave told reporters that the vast building was a “tactical nightmare” for first responders because of its numerous places for Alexis to take cover and hide.
Officials said it was NCIS agents who pulled a D.C. officer who was shot in the legs to safety and carried him down three flights of stairs and outside. The officer, Scott Williams, a 23-year veteran, was still at MedStar Washington Hospital Center on Wednesday but was expected to make a full recovery. Police also said that a second D.C. officer was hit twice in the chest but that his vest saved him from injury.
The shotgun was found on the first floor of Building 197, near the identification badge that had allowed Alexis access, court papers say.
Near Alexis’s body, authorities said, they found a 9mm semiautomatic pistol — which police have previously said was taken from a security guard he had killed in the first-floor lobby. The documents say the handgun was loaded, even after Alexis’s gunfire exchange in the final battle with police.
Among the items found inside the backpack were USB card readers, a USB memory stick, a copy of Microsoft Office, a DVD labeled “unclassified” and a disk for computer training. The affidavit does not say what authorities may have found on the computer disks or in the material. The FBI said they had also found other computer disks.