While the driving lights are the first use of a laser beam reflected off a mirror, the daytime running lamps, with their characteristic "torch" effect, and the indicator lights use LEDs.
So Starkweather fired a laser through the air between the two buildings, an improvised communications system that meant that, if you were driving down the Foothill Expressway on a foggy night and happened to look up, you might see a mysterious red beam streaking across the sky.