Four people were killed in a shooting on a train at the Forest Park Blue Line station in the early morning hours of Monday, the Chicago Tribune reports.
Police said they responded on early Monday morning to a 911 call claiming that multiple people had been shot at the station.
When police arrived on the scene, they found four people were shot, three of whom were pronounced dead at the scene. The fourth person died later at the hospital.
The alleged gunman "was no longer on scene and made good on their escape," the police said. They were able to use surveillance videos to find the suspect.
"That person was taken into custody and a firearm was recovered, authorities said, though it was not immediately clear if it was the same weapon used in the killings," the report said.
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This appears to be an isolated incident with "no immediate threat to the community," said a press release from the Forest Park police, which added that "anyone with information regarding these incidents is encouraged to contact the Forest Park Police Department Criminal Investigations Division."
The Forest Park station is a little over 10 miles from Western Springs, which was the No. 1 "safest and richest" suburb in the country, according to data compiled by GOBakingRates.
The Associated Press defines a mass shooting with four or more victims.