Navy Yard gunman kills 12; dead shooter was contractor

The normal buzz of the Washington Navy Yard's 3,000 workers will be replaced by the meticulous work of forensics teams, looking for answers after a military contractor gunned down 12 people and wounded eight others.

The installation is closed Tuesday to all but essential personnel. Investigators have questions to ask, measurements to take and information to sift through.

Mid-morning, Defense Secretary Chuck Hagel and other Department of Defense leaders will lay a wreath at the Navy Memorial plaza to honor the victims of Monday's shooting.

Dead is the gunman, Aaron Alexis -- a former Navy reservist with a "pattern of misconduct" -- and 12 others -- a mix of civilian workers and military contractors.

Authorities said Alexis was killed after an encounter with security. They gave no other details.

Alexis began at the Navy Yard last week, but worked at multiple Navy offices over the summer, said employer Thomas Hoshko, CEO of The Experts, an HP subcontractor. Hoshko said there were no reports of problems with Alexis at the other Navy offices.

Eight people were injured in the shooting, Washington Mayor Vincent Gray told reporters Monday night. Three of those were injured by gunfire, and the others had other types of injuries, such as bruises and chest pain. Earlier Monday evening, Navy Vice Adm. William D. French said 14 people were injured.

Authorities have recovered three weapons from the scene of the mass shooting, including a shotgun that investigators believe Alexis brought into the compound, The other two weapons -- handguns -- may have been taken from guards, the sources say.

Investigators believe Alexis rented an AR-15 but had returned it before Monday's shootings, the sources said. Authorities are still investigating how many weapons Aaron had access to, the sources said

"We still don't know all the facts. But we do know that several people have been shot and some have been killed," President Barack Obama said Monday afternoon. "So we are confronting yet another mass shooting. And today it happened on a military installation in our nation's capital."

Obama called the shooting a "cowardly act" that targeted military and civilians serving their country.

"They know the dangers of serving abroad," he said, "but today they faced the unimaginable violence that we wouldn't have expected here at home."