A woman was walking with two children southbound on Third Street at Williams Street at around 3:30 p.m.
The woman had a one child immediately with her and the five-year-old was trailing behind her as they crossed the street, according to police.
A private shuttle bus was driving eastbound on Williams Street and struck the boy as it turned right onto Third Street.
The shuttle bus had one passenger who was not injured and the driver of the bus was cooperating with the investigation, police said.
The cause of the crash has not been determined and police said impairment was not suspected. No arrests have been made.