Ren can hear the gunshot, but doesn't really see what's happening. He can faintly feel Eva's presence through their bond but that's it. At this point his vision was getting blurry and he could feel his conciousness fading.

Once Eva's close-by he tries to focus his gaze onto her, but failing to do so. She was just a blurry image.

"Eva... chan", his voice is very shaky and quiet. "I. Don't think... I'll make it..."

At least death wasn't permanent here. That's the only thing that gives him hope. That he'd come back in a few days all healed up. But it still hurt to die and he didn't want to.