The deceased, according to Forest Park Mayor Rory Hoskins, “were shot execution-style as they slept.”

Four individuals were slain “execution-style” in a mass shooting on a train in Chicago on Labor Day, prompting the charging of a 30-year-old man with murder.

In connection with the murders of three men—Adrian Collins, 60, and Simeon Bihesi, 28—as well as Margaret Miller, 64—Ranni Davis, 30, of Chicago, has been charged with four counts of first-degree murder.

At approximately 5.30 a.m. local time on Monday, the Forest Park Police Department received a call regarding three individuals who had been shot while they were dozing off on a CTA Blueline train.

When police arrived at the Forest Park CTA Blueline Station, they discovered four victims who had been shot.

NBC News said that Bihesi had several gunshot wounds, while Miller and Collins had both been hit in the head.

The office of the medical examiner reports that the other victim, a male who has not been identified, passed away due to multiple gunshot wounds.

After being recognized by Chicago police from surveillance footage on a different CTA Pink Line train, Davis was taken into custody approximately sixty minutes after the shooting, according to Fox 32 Chicago.

In a press conference, Daniel Pater, lieutenant in charge at Forest Park Police Department, said investigators had located the weapon used in the attack – a 9mm Glock 43 – and that it belonged to the suspect.

The Labor Day incident was branded as an isolated attack and police stressed the absence of an immediate threat to the Forest Park suburban community that houses 14,000 people.

Forest Park Mayor Rory Hoskins told reporters at The Associated Press that it was unlikely that the victims saw the shooter as: “They were shot execution-style as they slept.”

President of the Chicago Transit Authority Dorval Carter Jr. responded, “First of all, I can’t speak to the question of whether these individuals are homeless or not,” when asked if the victims were without a place to live.

“I believe the police and the state’s attorney will discuss that at a later time.

“I can tell you that, in terms of the homelessness issue itself, we have reached out to and supported more individuals on CTA than at any other time in our agency’s history,” the spokesperson said.

On Wednesday afternoon, Davis is scheduled to appear in court.