I think I found it:http://www.imdb.com/title/tt0079027/
"The Dark" - by John "Bud" Cardos
Even has Cathy Lee Crosby, Casey Kasem and Keenan Wynn in it!!!
So, no shoulder-mounted cannon .... it was lasers out of the eye. And looks like the city was LA, not SF .... I was close!!! ;)