Toby beamed when Peter used his cool ability to trap Sarah and use her as a shield. Really, the whole point of this to him was to get his big sister as much as possible, and to see the guy he considered to be a superhero come up with a way of winning made it that much better. "Good job, Peter!" He sprayed Sarah, focusing on accuracy at first but on speed when she started retaliating against Peter.
Then Monty started firing at everyone and even those simple rules didn't matter anymore. Toby started firing right and left, hitting more of the walls and ceiling than anyone participating in the fight.
His can empty, he tossed it away and all but dove into the middle of the fight to try to find another.