Laserblast

Teenager Billy Duncan wakes up in his bed, seemingly disturbed, and learns his mother is leaving for vacation. He is harassed by bullies Chuck Boran and Froggy, and by two police deputies who give him a speeding ticket. Billy discovers the laser cannon and pendant in the desert and uses it to shoot things. The two aliens land on Earth and begin searching for Billy. After killing a man and stealing his van, Billy goes on a rampage.