During her escape from the research facility, Selene jumps onto a driving truck.
The truck driver notices her, makes a full stop and she flies over the vehicle. The driver then steps out with a gun in hand, walks up to her lying on the ground and without blinking an eye, shoots her straight in the face.
That was the point where I was completely baffled. What the hell is wrong with this guy?
Maybe he had a bad day, ok. We all know those, but shooting someone cold blooded without even asking why she used his truck as a taxi?
You could argue that he is living in a pretty bad world with vampires and werewolves and you can never be too careful, but:
So why is he acting this way? Am I missing something?
I haven't seen the movie, but if it's a semi-truck, or a truck to haul any sort of cargo or materials, he could have thought she was trying to steal something off of his truck. Truckers tend to get pretty touchy about people messing with stuff on their trucks. This character could have just been a bit further on the touchiness scale than usual.
Underworld Awakening shows the humans capturing Selene during The Purge which was a crusade to exterminate the supernaturals. Selene is released from the cryogenic suspension and she escapes.
When Selene escaped the research facility, the driver of the truck shot her. The uniform of the driver may suggest something to do with security or involvement with the facility. The screenshot you posted shows the guy wearing a gun and an id, with a security-like get-up. So I'm guessing security.
Now if Selene was captured and held in the facility, and she escaped, whoever saw her would try to stop her. And that's what the guy was doing.
I don't remember the movie, so cannot remember if it was Eve or Selene.
On the other hand, Eve was injured and captured by some diseased Lycans, not Humans.