Pietro was drawn by the scream, trying to find somewhere on the grounds for a smoke break where one of the kids wouldn't be able to find him (surprisingly difficult as it turned out), and he peered out from round the corner of the building. He didn't see anything to scream about, just another X-brat, first edition, but Pietro didn't know if they were big on keeping in touch with one another, and he was quick to gesture to the school, and explain- "I work here now." All though, really, if he was still working for the Brotherhood, Beast wouldn't have seen him. It was a matter of pride.
[Ooc: I know you were probably hoping for one of the main x-men cast, that's why I held off tagging this, and if you would prefer to wait for one of them just let me know and I can delete.]