The article questions whether the snake "fell out of a moving vehicle". I doubt it, as the glass aquarium would have been smashed.
And "corral" the snake? It's a ball python. The guy is HOLDING him. You don't corral them, you pick them up--with gloves, like the officer did--and set him in the tank. They're making it sound like he kept poking him with a cattle prod to get him to go in the tank.
I think someone bought a baby ball python, and then peed their pants when it got to adult size and decided to abandon it by a busy highway. That's why the tank was there with the snake; it's the same scheme the people who leave puppies by the side of the road use. They know (or rather hope) that people will find the animals and take pity on them, and rescue them.
I guess it's just lucky for this snake that he was found in time, as it's cold here in Washington and he would've froze had he gotten far, and that the person who found him didn't freak out at the sight of the snake and chop his head off with a shovel.
http://www.krem.com/news/northwest-news/131916238.html