Chicago police announced five new murder charges against a man they say killed six people within a nine-month span in 2020 when he was a teenager.

Antonio Reyes, now 21, was charged with five felony counts of first-degree murder and four felony counts of attempted first-degree murder on Tuesday, Chicago Police Superintendent Larry Snelling said during a news conference the following day.

“This speaks to the level of disregard this offender had toward human life. It’s difficult to comprehend how anyone could easily take someone’s life, and especially so many in one year,” the police superintendent said.

Reyes was arrested in December 2020 and has been in custody at the Cook County jail since 2021, awaiting trial on other murder and attempted murder charges for the killing of a sixth person, a 26-year-old man in June 2020, officials said.

The five killings Reyes was charged with on Tuesday happened between March and November 2020, with the victims ranging in age from 16 to 31, police said.

Reyes was also charged with three counts of attempted murder for children between the ages of three and nine.

“These children were in a vehicle with the adult victim who was killed in a barrage of bullets,” Snelling said.

Two of the charges stem from the killing of a 21-year-old man at a gas station in April 2020 and an attempted murder charge of another victim, police said.

“One victim was killed when he went to the gas station to buy a pop early one evening,” Cook County State’s Attorney Eileen O’Neill Burke said.

“Another victim was sitting in a parked car with a friend on Palm Sunday afternoon when he was shot and killed.

“Another victim’s only crime was taking his family to buy a new puppy one afternoon. He was shot and severely wounded in front of his three children, and he succumbed to his injuries months later.”

While in custody, Reyes also allegedly tried to kill his cellmate with a shank, O’Neill Burke said.

“Not once have these detectives forgotten why they do this job,” Snelling said.

“They investigated these cases for more than four years in the memory of the victims, and the family members of these victims, and also our community members who have had to suffer through this trauma.”

Authorities say they have no evidence the victims were connected to each other and had not met Reyes previously.

Investigators have no reason to suspect Reyes “had any reason to target them,” the state’s attorney said.

The recovery of a 40-calibre handgun in summer 2020 provided a significant key in the investigation, helping detectives see a relationship to other scenes where similar casings had matched the firearm, police said.

Additionally, Reyes’ social media footprint was “fairly significant,” allowing detectives to link social media postings to some of the killings, according to police.

“We’re also going to continue to look at additional cases to see associates that he may have been with and their role in those incidents,” Chicago Police Chief of Detectives Antoinette Ursitti said.

Claudio Cassio, 21, was one of the six people Reyes is accused of killing.

His mother, Nohemi Cossio, told CNN affiliate WLS she continues to mourn the loss of her son.

“It’s been a long time coming. I almost felt like we would never see this day,” she said.

“It’s, you know, part of the healing process. And my son will have justice, along with all these other innocent victims.”

Reyes pleaded not guilty to all new charges brought against him this week at an arraignment Tuesday.

CNN is attempting to determine whether he has an attorney.

He is due back in court on March 18 for a detention hearing on these cases.

He is being held without bail, according to the state’s attorney office.