1st film: Did Jazz just sit there?

In the 2007 film, just after Sam notices that Bumblebee's legs have been blown off, is that Jazz parked behind him in vehicle mode? As Bumblebee crawls towards him, Sam tells the Jazz-looking car to "back up!" and the car does. If this is Jazz, why in the world would he just be sitting there doing nothing instead of helping the situation? (I realize that in the next scenes, he attacks Brawl, but still...)
Any insights?
Any insights?