4 people shot and killed on Chicago-area Blue Line train

CHICAGO (CBS) — Four people were killed in a mass shooting on a CTA Blue Line train in Forest Park on Monday morning.

Forest Park Police Deputy Chief Christopher Chin said all four victims were passengers on a Blue Line train as it was headed into the Forest Park terminal when they were shot shortly before 5:30 a.m.

Police said three victims were found dead at the scene. A fourth victim was taken to a local hospital and pronounced dead. Chin said the victims' ages and genders were not yet available as of 11:15 a.m.

Chin said the shooting appeared to be an isolated incident, and there was no threat to the community. Investigators believe there was only one shooter.

Police said it did not appear the shooter knew any of the victims, who all appeared to be homeless people riding the train. Police also said it did not appear that the shooting involved a robbery, and that the attack was completely random.

"This obviously is shocking. You know, it is uncommon here to have a mass shooting like this, especially this close to home that we're actually investigating on a holiday. So, for people to feel unsafe, it's justified," Chin said. "It's a horrible situation. It's definitely something that you don't want to wake up to. It's a Monday morning on a holiday. Everyone's supposed to be enjoying their time off, time with their families. It's Labor Day, so to actually have to be here to address a situation like this, it's horrible."

CTA security and Forest Park Police located the suspected shooter using surveillance video. The suspect was located on a CTA Pink Line Train and taken into custody later Monday morning. A weapon was recovered.

"Surveillance video is vital in a lot of our investigations, especially in this one," Chin said.

Blue Line service has been temporarily suspended between Forest Park and Austin. Shuttle buses will be available and CTA trains will operate between O'Hare and Austin.

"It's a horrible tragedy that four people are dead on Labor Day weekend," Forest Park Mayor Rory Hoskins said.

CTA issued the following statement:

"Although this was an isolated incident, this heinous and egregious act of violence should never have occurred, none the less on a public transit train.

"As soon as this matter was reported, CTA immediately deployed resources to assist the Forest Park Police in their investigation into the matter, including review of all possible security camera footage, which proved to be vital in aiding local enforcement.

"We commend both the Forest Park Police Department for their thorough and collaborative efforts to provide information to partner agencies; as well as the Chicago Police Department whose quick actions led to the apprehension of a suspect in this matter.

"CTA will continue to work with local law enforcement as part of this ongoing investigation."

Chin asked anyone with information on the shooting to contact Forest Park police at 708-366-2425 or detectives@forestpark.net .

This is a developing story. Please check back for new updates.