MINNEAPOLIS — Authorities are investigating why and how a van driver slammed into a crowded bus stop shelter in north Minneapolis on Tuesday, injuring at least six people, including three critically.

The crash happened at a busy intersection at about 9:30 a.m. Metro Transit spokesman Howie Padilla said the driver hit the side mirror of a bus that had stopped to unload passengers, then backed up, drove forward and hit the mirror again before driving around the corner and crashing into the shelter.