Suspect charged in shooting death of four passengers sleeping on Chicago train before attack

A man was charged Tuesday in a mass shooting that resulted in the death of four passengers on the CTA Blue Line train on Monday.

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

Rhanni Davis, 30, of Chicago, was charged with four counts of first-degree murder, according to the Forest Park Police.

Forest Park Deputy Chief Chris Chin said that a motive had not been determined yet.

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

Two of the victims have been identified as Simeon Bihesi, a 28-year-old man, and Adrian Collins, a 60-year-old man.