It's judgment day for bad continuity editors. Perhaps the director said, "I'll be back... to re-shoot this later on, because it isn't right", but just never had the time. Arnold Schwarzenegger is going to need your clothes, your boots, and a second take at this scene. The legendary film was light years ahead of its time in terms of special effects, and audiences were amazed by the shape-shifting abilities of Robert Patrick as the T1000.
Shooting the T1000 was a waste of time, because it just absorbed bullets and morphed itself back together again. Perhaps it also had a way of knowing danger was coming and getting out of the way, though, because in this scene it manages to split its own head open before Arnie even pulls the trigger. It's no use spending all that money on the latest CGI technology if you can't get the physical things right!