OAKDALE, Minn. (AP) — Police are trying to determine why a 34-year-old man randomly shot at passing vehicles in a suburban St. Paul neighborhood, wounding a female driver and killing her 9-year-old son.

A witness tells The Associated Press that the man identified by police Tuesday as Nhan Lap Tran of Oakdale, was nonchalantly walking down the block the night before when he began firing.

Nine-year-old Devin Aryal of Oakdale was killed. His mother, 39-year-old Melissa Aryal, was shot in the arm. A woman in another vehicle also was injured, but was expected to survive.

Police Chief Bill Sullivan says it appears Tran legally owned the handgun used in the attack, and that Tran has no apparent history of mental health issues.

Prosecutors were expected to file charges Wednesday.