I Forgot the Name of That ___! discussion

It was a paperback book I got from the library before 1995 (year I graduated high school, that why I remember) Humanoid aliens take over the world forcing the inhabitants to take refuge underground. A girl, late teens, is scavenging and is discovered by an alien he takes her as a companion (no romance, just odd friendship)while she is with him she discovers that he is the last of his kind and the video chats she's seen him have are all recordings. He's terribly lonely. In the end he lowers his body shield and she shoots him in the back of the head.
Than is all I remember. Please help!!! I've been searching for this book for a while w/out success.

*Ella* wrote: "Hmmmm....

Could it be: Warlock (Darkwar #2)

That's the only one I could think of now."

No, I looked up the synopsis and that's not it. I'm 85% sure it took place on earth in the future.