Jason just witnessed something that had the potential to traumatize him as Clementine lay on the ground. He had hoped that the bullets didn't penetrate her but the blood on the floor told him otherwise.
Jason's eyes darkened and the zombie didn't even know what happened but a blow landed right on its jaw, dislocating it but fracturing the bones beneath his fingers.
This was impressive due to the zombie's enhanced physiology.
The zombie stumbled to the ground and Jason knew he had to kill it or he wouldn't be able to attend to Clementine.
Jason mounted the zombie and began to pummel away at its face, he knew he needed to crush the zombie's skull.
The zombie was visibly distraught as it tried desperately to defend against the barrage of blows but Jason didn't relent.
It managed to kick Jason away but the force of the kick sent him tumbling back, crashing into the wall.