The crash happened around 12:31 p.m. near 152nd Street Park Avenue in Harvey, officials said.
The location is right next to Thornton Township High School, and emergency crews spent roughly eight hours on the scene investigating.
According to CSX Transportation, a vehicle drove past the lowered crossing gates and struck the side of a freight train.
All three people inside the vehicle died as a result of injuries from the crash, the spokesperson said.
32-year-old Keith A. Walker of Blue Island, Illinois, was identified as one of the three killed in the crash.
The video in the player above is from an earlier report.
RELATED | 3 dead after car crashes into train in Harvey, officials say
No one on the train was injured, CSX said.
It's still not clear what exactly led up to this or what caused the driver to bypass those crossing gates.
SEE ALSO | Man charged with DUI after bystanders pull him from car before being hit by train in Morton Grove
CSX said they are investigating the crash along with Illinois State Police and the Harvey Police Department.
Dolton police also responded to the crash, according to CSX, but Dolton police said they are not investigating the incident.