CHICAGO (CBS) — A man was charged Tuesday afternoon in a mass shooting that left four people dead on a CTA Blue Line train in west suburban Forest Park the day before.

Rhanni Davis, 30, of Chicago, is charged with four counts of first-degree murder, according to Forest Park police.

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 am

Police said three victims were found dead at the scene. A fourth victim was taken to a local hospital, where they died. Officials had identified two of the victims as of Tuesday afternoon—Simeon Bihesi, a 28-year-old man, and Adrian Collins, a 60-year-old man.

The Cook County Medical Examiner’s office said one of other two victims was a 52-year-old man and another was a 64-year-old woman.

CTA security and Forest Park Police found 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.

Police said the shooting appeared to be an isolated incident.

Police said it did not appear the shooter knew any of the victims, who all appeared to be sleeping while riding the train. Police also said it did not appear that the shooter tried to rob the victims and that the attack was completely random.

A news conference with further information on the charges is set for 7 pm Tuesday.

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