Peter wasn't just hoping he didn't get shot for his own safety, but he was terrified for Iris. He didn't know what she'd do if she actually hit him. He didn't even want to think about it, and he wished there was another way of handling this.
He didn't know what else to do but stand there and take a deep breath and watch Iris, hoping his body language was as relaxed as possible. This would all be over soon one way or another, and he could just breathe through it. He didn't flinch with his whole body at the sound, but he was startled by it, it was almost like the anticipation of knowing it was coming made the sound all much louder.
But he wasn't hit. When it was all said and done he wasn't hit. He smiled at her and crossed the room slowly, "Iris, it's alright." he said calmly.