A teen girl was hit and killed by a vehicle driven by an off-duty New Jersey State Police Trooper, prosecutors said Sunday.

The high school freshman, identified as Theresa Di Falco, was found unconscious on Central Avenue in Westfield about 8:30 p.m. Saturday and pronounced dead at the scene.

The Union County prosecutor said Falco was hit by a service vehicle driven by an off-duty New Jersey state trooper.

Falco was "a really well loved and well liked kid," said Betsy Laskaris, who knew her family.

Jonathan Saminski, who went to school with Falco, said she was taking part in a scavenger hunt that started at his home.

He said that speeding was a common problem on the street.

An investigation is ongoing.

Grief counselors would be available at Westfield High School on Monday, principal Derrick Nelson said.

Anyone with information regarding the crash is asked to call Sgt. Jose Vendas at the Prosecutor's Office at 908-358-3048 or Westfield Police Lt. Jason McErlean at 908-789-6068.