Agree totally. I keep thinking what is his end game here? Say he does hole up for 6 months, a year, whatever, then what? He'd have to try to get a new identity somehow. How does someone do that?
I find this one of the more intriguing questions. For some reason, I doubt he has a passport (and no chance of getting one now). But if he does have a passport, I do think there are (illegal) ways for him to flee the US to either Canada or Mexico. I think Canada would be prompt in catching him if he tried to fly out of Canada though. So he'd have to go on the lam. In Mexico, he could keep traveling south and would probably find a local airport (I can think of a couple) where he could catch a flight (Cuba won't work - need very specific visas to board a plan or ship to Cuba) or get on a ship (better idea).
(Long post follow...TL;DR...there are several ways to get a fake passport).
I know someone who fled the US and joined the Merchant Marines in Panama. He used his regular ID, no one checked. He lived that way for 2 years before deciding to come back (statute of limitations had run out - it was a fairly minor crime compared to this). I know another person who went illegally into Mexico and couldn't get back (US denied him entry due to various reasons) and spent a year in a legal battle to prove he really wasn't intentionally breaking the law and was in fact a US citizen. I know someone who had a passport already and walked over the border and flew from Juarez Intl to someplace in Europe, where he lived for a year. He was not wanted by LE, but he was attempting to avoid all contact with his parents over a specific situation. I could keep going. As an anthropologist with experience in Mexico and specifically in border towns, these people (or their families) have contacted me for help - I know some people in the FBI who have helped me understand the in's and out's of some of this. This is not an exhaustive list of people I know who have fled.
Getting a new identity is not that difficult if you know a few criminals. Heck, four houses away from me, two people were busted for procuring fake identification. And at one DMV in California, people were busted for accepting bribes to issue fake ID's. In Downtown LA, you can buy them if you know what you're doing. My own identity was stolen about a decade ago, which I found out when I didn't receive my DL renewal notice (someone had changed my address for me and had a replacement DL sent to Texas, where they were also using my credit card from time to time - the bank merely reimbursed me, the DMV asked me for proof of address and reissued the right license - to me; now I have it calendared when I'm supposed to get the renewal notice!)
(I believe the renewal notice was stolen from my mailbox and that we have the person on camera, but the time/date stamp was not correct and the police had no interest in viewing that video whatsoever - they told me to get a locking mailbox, which we did).
Of course, I've lived all my life in a big metropolitan area, so my experiences are not all that unusual. My ex-husband had his identity stolen early in his university years (by. someone with the same name) and unknown to him, that person got a CA DL using his name and my ex's current address - while using his own birth certificate). It was a nightmare getting it straightened out. The guy was wanted for a few property crimes - we found that out when we were screened for a rental and told that my ex was a criminal - not true!)
Someone tried to steal my dad's identity (older people are victims of this all the time) and got a copy of dad's SS card. Once a person gets one valid piece of idea, the next one is easier to get. Actual passports are hard to counterfeit but those passport cards are not so hard - and those can be purchased.
All that being said, a person has to be a determined criminal and of a criminal mind to do this. Seeing no evidence that Brian or his parents fall into the category, I am assuming he'll hide out in the US for a long time. He can hitchhike. He can change his appearance. He probably looks nothing like the photos being shown everywhere on SM at this point in time.