He had been suffering a host of serious mental problems, including paranoia and a sleep disorder, and had been hearing voices in his head, the officials said.
The assault is raising more questions about the adequacy of the background checks done on contract employees and others who are issued security clearances — an issue that came up most recently with National Security Agency leaker Edward Snowden, an IT employee with a government contractor.
Navy Secretary Ray Mabus ordered two security reviews Tuesday of how well the Navy protects its bases and how accurately it screens its workers.
A senior defense official also said Defense Secretary Chuck Hagel intends to order a review of physical security at all department installations worldwide.
Also, the House and Senates Veterans' Affairs Committees have asked the VA for details about any treatment provided to Alexis.