I don't think it is a disguise. Vagrants layer up, have facial hair, and long hair, because they are exposed to the elements. They also don't have access to hygiene supplies and facilities. I'd bet he left behind a camp LE found along with a lot of human waste=dna.
The below is merely jumping off your post to add more thoughts.
There was a mention by LE that he could have changed his appearance. IMO, they meant after the crime, not before.
Now LE is looking for information on a hitchhiker.
This guy looks just like the vagrants I used to run into on a biking trail I used to ride. I also lived in an area with lots of homeless. I carried a gun at all times. IMO, the POI in this case is of the group that sole purpose is to stay hidden. Their goal is to remain invisible at all costs. Even if they had money, they would still break into houses and businesses while they are empty. To steal what they need, food, liquor, drugs, booze. And while there they may make a sandwich and take a shower. They won't go into town our shop at a store.They do, from time to time, react impulsively and make a public appearance. Which I think happened in this case. The opportunity presented itself and he reacted. He may have even been laughed at by the girls and it pissed him off. I've seen that as well.
Whether the bridge is level or not, his gait is exactly like the vagrants I observed. They can't even stand still when standing still. Years of Alcohols and drug use has usually left them with neurological damage that causes their body to move oddly, even when they are sober.
I would love to look at the area crime logs for Breaking and entering and thefts.
Just my thoughts for the day.
Confusion, thanks for letting me jump off your post.