This booking photo provided by the Fort Worth Police Department shows Aaron Alexis, arrested in September, 2010, on suspicion of discharging a firearm in the city limits. The FBI has identified Alexis, 34, as the gunman in the Monday, Sept. 16, 2013 shooting rampage at at the Washington Navy Yard in Washington that left thirteen dead, including himself.

WASHINGTON - Hewlett-Packard Co. says it's severing ties with a subcontractor that employed Washington Navy Yard shooter Aaron Alexis.

An HP spokesman said Wednesday that the Florida-based firm The Experts failed to respond appropriately to the Fort Worth, Texas-area man's mental health issues. It also said HP had strict policies for its contractors and required them to adhere to high standards.

An August police from Rhode Island said Alexis complained voices harassed him through a hotel wall.

The Experts said it ran two background checks on Alexis that turned up only a traffic violation. It also said the Pentagon confirmed twice that Alexis had a valid security clearance.

Alexis began working at the Navy Yard this summer refreshing computer systems. He killed 12 people on Sept. 16 there before police killed him.