A dump-truck driver who ran into the back of group of motorcycles last month, killing four riders, was on methamphetamine at the time of the collision, Phoenix police say.
Eight motorcycles were hit; four people were killed and five were injured.
Police arrested Michael Jakscht, 46, today after he allegedly drove away from his Scottsdale house while impaired.
Jakscht already had been under surveillance since the March 25 collision, which occurred on the Carefree Highway near 27th Avenue.
An expedited drug test revealed the meth in Jakscht's system, cops said.
Police plan to book him into county jail tonight and seek charges of four counts of manslaughter, five counts of aggravated assault, and seven counts of endangerment.
Jakscht's Facebook page describes him as single and self-employed.
Police expect more charges to be filed as the investigation continues.