Four passengers shot on train in Chicago area appeared to be asleep before attack: Police

The four people who were fatally shot on a commuter train in the Chicago area on Monday were apparently asleep in their seats just before the attack began, according to a police review of security footage.

Forest Park Deputy Chief Chris Chin said a suspect has been taken into custody and their weapon was recovered but a motive has not been determined yet.

The victims have not been officially confirmed and the police haven't released the name of the suspect.

"This appears to be an isolated incident on this unfortunate day," Chin said. "It's a horrible situation."