Okay, there it was: that strange groaning sound. Why did they groan? From a practical standpoint, all it did was give away their location, and while it was certainly unsettling, it didn't seem to give the zombies much of a combat advantage.
Pietro turned, became a moving streak of color, and reappeared next to a staggering zombie who'd been moving in on Simon. The bat swung, connecting with an already battered head. It looked as if the zombie had lost an ear at some point - perhaps to another zombie.
If he'd been in a joking mood, there was probably a baseball wisecrack to be made. Unfortunately? Pietro didn't have much of a sense of humor, most of the time.
The zombie went down, so the X-Man began to trot (at human speeds) towards the fleeing Simon. He looked as if all of his limbs were intact, and he wasn't moving like the undead, so Quicksilver took a chance and hailed him. "Hey," he said. "You're headed towards a swarm of them. About twenty, all gathered around a stalled city bus."