EXCLUSIVE

The "friend" James Howell -- who was arrested with an arsenal before L.A. Pride -- had driven cross-country to meet ... was just a guy he met online, and not an accomplice to a potential crime ... according to law enforcement.

We're told Howell originally told police he was meeting a friend and going to the parade -- leading cops to believe that person could be a threat to the public.

Law enforcement sources say they found the friend and he backs up Howell's story, but is adamant he was clueless Howell's trunk contained 3 assault rifles, high capacity magazines, and a 5 gallon bucket of chemicals cops suspect could have been used as a bomb.

We're told the friend told police he met the Indiana man online recently, and planned to meet in person to attend Pride together ... and that's all.

Cops believed the alibi ... and cleared him of any involvement.

However ... it's still a mystery as to what exactly, if anything, Howell had planned. We're told he's not budging during questioning. He remains in custody on $500,000 bail.