Bruce's heart slammed dangerously fast in his chest as Loki reacted to the threat. Blood wasn't anything new, Bruce had seen his fair share of it, but it didn't keep him from being stunned that the first and last blow was fatal, and delivered by Loki in a single, solid punch. The past several days had been spent trying to help people who were sick, and that's exactly what the man, now dead, was.. before Loki put his fist through his chest. Bruce didn't doubt for a second that he would have taken a hit, and been put at a higher risk of infection had Loki not intervened. It didn't make it any easier to unclench his jaw.
Looks like Loki's debt had been paid.
Just as Bruce was successfully willing himself to calm down, he was in also in the midst of trying to form words, ready to back away from the now dead body, he noticed Loki's sudden pause in the middle of his turn. Bruce's eyes widened with alarm, and he shifted his weight further to the side to get a better look at Loki. It was obvious he very suddenly wasn't feeling right, and Loki only confirmed the obvious. The decision that Bruce made wasn't a hard one, but it was quick.
Muscle and bone shifted the very moment Bruce threw the punch. By the time it landed, it was all the Other Guy, and he gave no warning. He swung fast and hard, just as usual, and every punch followed another until Loki was on the ground, unconscious and no longer a threat. All the residual fear that carried over from one state of consciousness to the next escaped in a short, ferocious roar. After The Hulk punched the ground for good measure, he grabbed Loki by the ankle and began dragging him back towards the base in silence.
[ooc: SO SO SO SO SO sorry, I thought I replied to this!]