Before Mitch could deny the claim of murder with a strong, "I WAS NOT TRYING TO KILL YOU," he had realized two things: 1) That Sal really seemed to like Mitch's head and gut as targets, a practice that was getting tiresome for the young man very fast; and 2) That Sal wasn't burned.
Sal wasn't burned. He had just stood there, directly in the line of fire, and he wasn't even singed.
Since Mitch didn't have time to react to the slap, the air was once again knocked out of him. A string of swearwords followed the escaped air, even though he knew they wouldn't do him any good. The Asgardian then grabbed Sal's wrist, since his hand was still holding the collar of the shirt, and twisted it as hard as possible, while engulfing both of their hands and arms in flames.
He vaguely remembered saying to Alessa that he only used fire as a last resort. This was definitely a last resort situation.