The 3-year-old son of a firefighter was struck and killed at a memorial walk in Delaware.
The incident happened just before the event was set to start.
Firefighters, friends and family had gathered in Wilmington over the weekend to honor the lives of three firefighters killed in the line of duty on the same day seven years ago.
Capt. Matthew Marsella of the Wilmington Fire Department said an off-duty firefighter was attempting to park for the event when he struck another firefighter's 3-year-old son with his vehicle, according to The Associated Press. The child was transported to Wilmington Hospital, where he was pronounced dead.
The names of those involved have not been released.
The Wilmington Police Department is investigating.
Wilmington Mayor Michael Purzycki said he was "profoundly saddened" by the "devastating incident."
"On an already somber day marking the seventh anniversary of the loss of three city heroes — Lt. Jerry Fickes, Capt. Chris Leach, and Lt. Ardythe Hope — the WFD once again found itself heartbroken and mourning a life taken much too soon," the mayor said in a statement. "There is, of course, no greater pain than that of a family dealing with the death of a child, and I join the entire City of Wilmington in extending my deepest condolences to the family as they grapple with this agonizing loss."
Leach and Fickes of the Wilmington Fire Department died battling a house fire in September 2016 when the first floor of the home collapsed, AP said. Hope was in critical condition for weeks before succumbing to her injuries.
The person accused of setting fire to the home, Beatriz Fana-Ruiz, pleaded guilty in 2019 to second-degree murder, arson and assault, AP said. She received a 30-year prison sentence with possible deportation to her home country of the Dominican Republic.