Tobias' screams had confirmed in Simms' mind that he would kill the struggling young man. He knew by now that the screams carried throughout the prison, and he could only hope that his eventual gurgling and gasps carried, as well. He was still expecting that Tobias might surrender. He wasn't expecting him to fight back.
There was a second where Simms thought that Tobias had just punched him in the throat. He dropped him instinctively, moving to bring a hand up to his throat as if that might help him catch his breath, while the other went out to try to catch Tobias' hand. It was the burning feeling that tipped him off at first. He had been punched before. This wasn't that.
The blood in his mouth brought him up to speed. Simms wheezed, trying to get air properly, and finding he couldn't. He tried again to push Tobias off of him, but by then Tobias had brought the knife down on him twice more, the second time drawing a spray of bright red blood out of him. He stumbled back, still gasping, fumbling to grab a knife from the counter, but only managing to knock one of those poisoned sandwiches to the ground.
Simms hit the ground shortly after. His knees had buckled, and he kept a hand on his throat as he tried to crawl backwards. Away. This wasn't supposed to happen like this. This wasn't supposed to happen with him.