Phantom From Space

The film starts out with an unidentified object hurtling from Alaska to the California coast, where the object seems to disappear. Mobile communications folks are sent out to determine the source of interference suddenly wreaking havoc in the area, and these guys keep bumping into cops investigating murders and other acts of destruction. Soon, these different forces team up with an army man and a scientist, and everyone eventually comes to the amazing conclusion that the source of all the trouble is actually a humanoid not of this world. The ending is not exactly a bright and chipper one, but it is just about the only plausible ending possible and, in it's own way, it works pretty effectively.