Thanks For Scaring Me For Life Grandpa

My colleague Shannon (a guy so there is no confusion) from Canada told us this story in the morning and I just had to pass it along.
So, Shannon gets to work a bit early and the doors are not yet unlocked. Two students and the Grandfather of one of them had also arrived early that day and they were all waiting out front together. Seeing that Shannon spoke a bit of Chinese the Grandfather asked a few questions about the class, the upcoming midterm, and his Grandsons general performance. Then for seemingly no reason he pulls out a baggy from his pocket and says to Shannon,

Grandpa: See, it's his underwear. (as he holds it towards Shannon)
Shannon: oh.
Grandpa: He was wearing them today but it's too hot so I told him to take them off.
Boy: I only said it was hot on the bus because there was no A/C.
Grandpa: (ignoring his grandson) Kids these days (he says with an eye of confusion)
Wearing underwear when they know it's so hot out.
(meanwhile the boy who was sitting next to him discretely begins to move away as he
realizes the only thing separating him from the other boys peepee is a thin layer of khaki)

The poor 13 year old was mortified.