A Michigan prosecutor says he still doesn't know why a man randomly killed six people in between driving for Uber around the Kalamazoo area in 2016.

Jason Dalton pleaded guilty to murder and attempted murder Monday , a day that was set aside for jury selection in his trial. He was a driver for Uber when he shot strangers in between picking up riders.

RELATED: Gunman pleads guilty in 2016 Kalamazoo shooting rampage that left six dead

Kalamazoo County prosecutor Jeff Getting says the motive remains a "key question" that haunts investigators. He says: "Everybody wants to know."

Dalton told police that the Uber app was controlling him on the day of the shootings. He was found competent to stand trial and had dropped plans for an insanity defense.

He now faces life in prison.

Dalton trial - victim family members
Victim family members react as Jason Dalton pleads guilty to six counts of murder and several other charges at the Kalamazoo County Courthouse on Monday, Jan. 7, 2019 in Kalamazoo, Michigan. Dalton, who was driving for Uber at the time shot eight people killing six of them, on Saturday, Feb. 20, 2016. Opening statements in the trial were scheduled to begin Tuesday, Jan. 8. (Joel Bissell | MLive.com)
Joel Bissell | MLive.com

â–ºMake it easy to keep up to date with more stories like this. Download the 13 ON YOUR SIDE app now.

Have a news tip? Email news@wzzm13.com, visit our Facebook page or Twitter.