Wal Marty

This is about one of my mother's handicapped clients.
She would die of mortification if she knew I was writing this.

My mother(Katsmom) took 2 of her handicapped clients to Wal-mart. It was their reward for behaving (not swearing, taking their meds, and not punching anyone). J. is mostly nonverbal (except for swear words) and very violent. Sam is quiet and pretty nice most of the time. Sam and J pick out cough drops and white socks for their reward. They get up to the check out. Like most Wal-marts, there are 2 check outs open and 50 people waiting in line.
After 10 min. they are 1 person away from checking out. Sam puts his cough drops on the belt and then turns to my mother(who is trying to apologize to the nice check out lady--when J. called you a f-ing titty-ho--he meant to say 'Hello, how are you today?')

Sam: Katsmom?
Katsmom: Yes, Sam. What is it? No J. do not punch that little boy!
Sam: If I tell you something will you get mad?
Katsmom: What Sam? I won't get mad.
Sam: I'm afraid you'll get mad.
Katsmom: No, I won't get mad.
Sam: Are you sure?
Katsmom: Yes! What is it!
Sam: I had to go to the bathroom.
Katsmom: Well, can you wait a second? We're almost checked out. No! J. come back here!
Sam: No, Katsmom, I had to go. I had to. You're not mad are you?
Katsmom: What? What do you mean?
She looks down, checks his crotch for a wet stain. Her eyes travel down to the floor, to a small pile of poop that is spilling out of Sam's pant leg. Sam moves his leg and the pile of poop grows, spills over his shoe and then continues piling out of his pant leg. There is now a softball sized pile of poop on the floor and 20 people watching from the line behind my mother. The clerk gives her a handful of paper towels and my mother picks up the poop and deposits it in a handy wastepaper basket.
Then she takes her clients and runs out of the store.
She refuses to shop there ever again.

My question after this story was, "How could he do that? Wouldn't the poop get stuck in his underwear?"
I guess he wears loose boxers.