With a derisive snort in reply to Derek's greeting, Stiles looked to the two that had suddenly joined him in the hallway, nodding to Shauna and eyes lingering on the guy he didn't recognize. How the hell should he know how many people were at the school after hours - couldn't Derek use his wolfy senses to listen out for other heartbeats or something? Stiles suddenly wished that Scott were there - they always had each other's backs, but he suddenly felt very vulnerable in the context of things.
"Oh yeah, I'd love to just get out of here, but if whatever did that to you is still in here, what's to stop it from getting one of us?" he laughed, arms moving to remove the flannel layered over his shirt. He balled the shirt up, dropping to his knees to press the fabric to the deep wound in Derek's thigh - careful to avoid touching too much of the werewolf, but pressing firmly to try to prevent any more loss of blood. "Dude, aren't you supposed to heal?" he whispered to Derek, glancing from him to the other two teenagers. "Guys, we might need to move him, I'm gonna need some help." He wasn't above leaving Derek here by himself — it's not like he had a reason to do anything otherwise, but the hairs on the back of his neck were standing on end, and he knew that if something was lurking around powerful enough to injure a werewolf, then they'd need Derek's help.