Debris sits in front of the last known address of Aaron Alexis Monday, Sept. 16, 2013, in Fort Worth, Texas. Police have identified Alexis as the gunman in Monday's shooting rampage at at the Washington Navy Yard in Washington. Mayor Vincent Gray said at a news conference Monday afternoon that Alexis was among the dead. (AP Photo/LM Otero)

WASHINGTON (Reuters) - Aaron Alexis, the 34-year-old suspect in Monday's shooting rampage at the Washington Navy Yard, had "secret" clearance and was assigned to start working there as a civilian contractor with a military-issued ID card, his firm's chief executive told Reuters.

"He did have a secret clearance. And he did have a CAC (common access card)," said Thomas Hoshko, CEO of The Experts Inc, which was helping service the Navy Marine Corps Intranet as a subcontractor for HP Enterprise Services, part of Hewlett-Packard Co.

Alexis, of Forth Worth, Texas, is suspected of opening fire at the Naval Sea Systems Command building in the Washington Navy Yard in a shooting that left 13 people dead, including the shooter.

Asked when Alexis was supposed to start work, Hoshko said in a telephone interview: "That's what I got to find out, if he was supposed to start today ... It's not clear to me."

Hoshko said he was unaware of any issues with misconduct involving Alexis or any possible grievance that could have led to the shooting.

Alexis had previously worked for The Experts in Japan from September 2012 to January 2013, he said.

"We had just recently re-hired him. Another background investigation was re-run and cleared through the defense security service in July 2013," Hoshko said.

Hoshko said he believed that Alexis' "secret" security clearance dated back to 2007.

The Navy said Alexis enlisted as a full-time Navy reservist in May 2007. He was discharged in 2011 after a series of misconduct issues, a Navy official said.

(Reporting by Phil Stewart; Editing by David Brunnstrom and Eric Walsh)