WASHINGTON (Reuters) - A California man who was fatally shot after opening fire on security officers outside the Pentagon appears to have been acting alone, with no links to domestic or international terrorism, police said on Friday.

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The gunman, identified by authorities as 36-year-old John Patrick Bedell, was apparently trying to gain entry to the giant U.S. Defense Department headquarters when he approached a security checkpoint and started shooting, police said.

He was shot in the head on Thursday evening near the main entrance to the building in a shootout with three security officers, two of whom received “superficial” bullet wounds and were treated and released from a local hospital, Pentagon police chief Richard Keevill told reporters.

“There is no indication at this point that there (is) any domestic or international terrorism nexus to this at all,” Keevill said. “... There doesn’t appear to be anyone else acting in concert with Mr. Bedell.”

Keevill said authorities do not know Bedell’s motives in the shooting, which occurred at the Pentagon entrance near a busy commuter rail station. But Keevill said authorities are looking into a series of Internet postings by a user identified as “JPatrickBedell” for clues.

These postings make reference to U.S. marijuana laws and marijuana-related felony charges in 2006 in California against John Patrick Bedell. They also refer to the September 11, 2001 attacks against the United States and the case of a U.S. Marine Corps colonel who died in 1991.

Keevill said authorities had not yet determined whether those postings were made by the gunman.

People can approach that entrance to the Pentagon unimpeded from the Metro station. The shootout occurred at a security checkpoint.

“He was very well armed. I will tell you he had two 9 mm semiautomatic weapons and many magazines,” Keevill said.

He added that the man’s car that he drove from California has been located, and that it contained more ammunition. Keevill said there is a surveillance video showing the suspect that “pretty much confirms what we’ve been saying, that he acted alone.”

Instead of presenting a Pentagon pass, which is required to enter the building, the gunman pulled out a gun, Keevill said.

The underground Metro station is adjacent to the main entrance of the Pentagon in Arlington, Virginia, just across the Potomac River from Washington.

The Pentagon was one of the targets in the Sept 11 hijacked plane attacks. One of the planes smashed into the U.S. military headquarters, killing 125 people, along with the plane’s 59 passengers and crew and the five hijackers.