KALAMAZOO, Michigan — An Uber driver admitted his involvement in a Saturday, Feb 20, night shooting rampage that left six people dead and two others injured, the county prosecutor said on Monday, Feb 22, as the driver was formally charged with murder. But the motive of the man, who had no criminal history, remained a mystery.

Jason Brian Dalton, 45 has been charged with six counts of murder in the nearly five-hour rampage. According to detectives, Dalton told them he “took people’s lives.”

Police said Tuesday that Dalton did not have a history of mental health issues. And on Wednesday, Kalamazoo Public Safety Chief Jeff Hadley told CNN that Dalton legally bought the 9mm handgun he allegedly used in the shootings, though he did not have a concealed pistol license.

Dalton earned an associate’s degree in law enforcement from Kalamazoo Valley Community College in 1992, the school said Wednesday. Records show Dalton enrolled at the college in 1989, said Mike Collins, the college’s executive vice president of academic and student services.

President Obama weighed in, as he has many times after mass shootings, arguing in a White House appearance that it should be harder for troubled people to obtain guns. “I’ve got to assume all of you are just as tired as I am of seeing this stuff happen in your states,” he said.

Left dead or dying were Mary Jo Nye, 60; her sister, Mary Lou Nye, 62; Barbara Hawthorne, 68; and Dorothy Brown, 74. A 14-year-old girl was pronounced dead and placed on a ventilator while plans were made for organ donation, Lieutenant Hinz said, but more than an hour later, she squeezed her mother’s hand. She remained in intensive care on Monday.