Washington Navy Yard shooting: Latest developments

WASHINGTON (CNN) -- Details are emerging on Aaron Alexis and his chaotic morning of violence that left 12 people dead at the Washington Navy Yard on Monday. But more questions remain. Here are the latest developments:


Open to essential personnel

-- The Navy Yard crime scene continues to be active and is only open to essential personnel, according to spokesman Ed Zeigler.

-- Access to Building 197 -- the site of the shooting -- is still be prohibited.


Sequence of events

-- When Alexis entered the building, he had a small bag believed to have contained a disassembled Remington 870, a federal law enforcement official says.

-- Alexis was seen on surveillance video ducking into a bathroom with the small bag and exiting with the shotgun.

-- He also had '00' buckshot shells, each packed with about a dozen pellets capable of causing tremendous damage.

-- Denise Robinson, who works in Building 197, told CNN's "New Day," on Wednesday that she saw the shooter and remembers his "cold stare." "He looked very calm and composed. He didn't look like a person that was angry or doing that type of event."


Security clearance questions

-- A senior Navy officer told CNN's Jake Tapper that Navy officials knew about Alexis' 2004 arrest for shooting out the tires of a car, but they decided to grant him security clearance anyway in 2007.

-- The officer says the investigators knew of the incident and interviewed Alexis but decided it did not preclude granting the clearance. He "should have been screened out early in his enlistment," one expert says.

-- Mert Miller, an Office of Personnel Management official, said the agency conducted a "background security clearance investigation for Aaron Alexis in 2007, and the Department of Defense adjudicated his file and granted his security clearance in 2008."

-- The agency is working with the Office of Management and Budget and the Director of National Intelligence "to review the oversight, nature and implementation of security and suitability standards for federal employees and contractors," Miller said Tuesday.

-- "In general, background security clearance investigations include information about an individual's criminal history, including criminal records, and that information would be passed on to the adjudicating agency," said Miller, associate director of OPM's Federal Investigative Services.


A somber milestone

-- The families of the Sandy Hook shooting victims will visit Capitol Hill today to mark nine months since the tragic mass shooting at Sandy Hook Elementary School in Connecticut . They also will call on Congress to act on legislation to reduce gun violence.

-- The visit was scheduled before the shooting at Navy Yard occurred, but it's safe to say the event will receive more attention in light of the week's events.


Who are the victims?

-- They were civilians and contractors, just starting their day at a massive military compound that's normally a bastion of safety. But for reasons that may never be known, former Navy reservist Aaron Alexis cut their lives short. Our profiles on the victims.