He was no longer an active duty Marine. That is a false story put out by his mother to gain sympathy for his case. He was discharged in 2012, he was still in the inactive Individual Ready Reserve. He did not get orders to active duty, he got a letter to report for his one day administrative meeting likely because he didn't notify the government of his change of address.
He was not going to college. He had dropped out.
He was not legally carrying the firearms in his possession. He imported an AR15 into California that was not in legal configuration, with hicap mags. As he wasn't a California resident it was likely the AR15 wasn't registered as required in California.
He was carrying a .45 caliber pistol unsecured in his vehicle cab, as a non-California resident if he had a Florida CCW it would not be recognized in California so he could have been sitting in a California prison.
He lied about never having been in Mexico before, he had been there several times. He had checked into a Tijuana motel earlier in the day.
He had mental issues according to his mother.
According to him in interviews I have listened to and interviews of his mother, he had a severe drinking problem. His drink of choice was bottles of vodka.