Sal had expected something to go wrong because no matter how desperate the situation looked, Mitch never did as he was told. And to think, Sal had actually considered being honest about his promise to leave Asgard alone...
None of the bullets struck him, thank his lucky stars. Banru's spell was impeccable, but Sal never expected anything to be perfect. Still, he knew his plan was ruined the moment Mitch had defied him. While the sound of weapons firing inside of Niflheim wasn't uncommon (really, it would be strange if it wasn't an almost daily occurence), it was certainly enough to startle Midvalley and Jazz. And there they were, Midvalley in the doorway and Jazz standing right behind him, cannon loaded.
This was the part where Sal's pride saved Mitch's life. Sal knew that he could have easily twisted the situation, to boldly declare that he caught Mitch sneaking in to kill Jazz and Midvalley and he'd come to stop him. It would have worked because the boy was on enemy soil and was holding a gun in his hand. But Sal had no intention of giving Mitch the credit and was also not ashamed to let them know his true intentions.
"Well, fuck, you just had to go and ruin the party, didn't you." Sal raised his gun at Mitch and fired it, the bullet striking the boy in the shoulder. Then he came up to him and pushed the firestarter out of the way and grabbed Midvalley by the front of his shirt.
Sal pressed his gun between Midvalley's eyes and then glanced up at Jazz coyly. He grinned at the giant robot, despite the cannon glaringly staring him in the face. "Is this the part when I get to say 'Game Over'?" Sal knew Jazz would know what he meant by that.