CHICAGO (WLS) -- Handguns in the wrong hands can be dangerous enough, but there is a new threat underway with lethal weapons even more easily available because some are concocted right at home.
Some criminals rely on 3D printers to alter pistols and transform them into fully automatic weapons.
In Lake County, Illinois, crime scenes covered with dozens and dozens of shell casings reveal that modified guns are becoming a regular threat for police and the public.
"We have crime scenes now with up to 90 or 100 shell casings. It's reasonable to believe that more innocent people would be injured because of the lack of control of the firearm when it's fully automatic," said Sgt. Matthew Harmon with the Lake County Special Investigations Group.
In June 2023, 14-year-old Pierre Johnson was killed in a hail of gunfire in the Fuller Park area. Video obtained by CWB Chicago shows armed suspects rapidly shooting after turning the corner of a building.
Attacks like that can be made possible by a tiny, Lego-like device called a switch.
Tharea Johnson is still grief stricken at the loss of her son and dumbfounded by the firepower now plaguing Chicago neighborhoods.
"You got 100 bullets shot in seconds; not minutes, seconds," she said. "How do you get this gun? Where do you buy it?"
The switch instantly changes a semi-automatic pistol into a machine gun-style weapon, and is the cause of what some in law enforcement are now calling "an evil arms race."
Will Panoke, an Assistant Special Agent in Charge with Chicago ATF, said the creation of these devices on 3D printers has escalated this to a new plateau.
"It has absolutely, because of the accessibility of 3D printers and the ease of creating these pieces within an hour or so and being able to affix those onto firearms within a matter of minutes, has really caused a serious problem for our communities," he said.
The ATF provided the I-Team with time lapse video that shows the easy birth of an illegal gun switch. ATF data reveals a six-fold increase in seized switches across the country the past five years.
And an I-Team analysis reveals a significant jump in Chicago arrests linked to modified guns the past several years.
There have been almost 1,000 arrests in each of the past two years. Juvenile arrests were seven times higher in 2022 compared to 2020 and the majority were 17-years-old.
The surge in modified guns is on display in the well-hidden sheriff's vault in north suburban Lake County, Illinois where the I-Team was invited to see some of the weapons gathered in the new arms race.
Sargent Matthew Harmon with the Lake County Special Investigations Group, said offenders caught with gun switches vary in age.
"I would say primarily the demographics are late teens to mid to early 30s that were seeing them. Many of them are involved in other crimes that we investigate and they possess these weapons as well," he said.
Tharea Johnson said her son is proof that the new gun war can't be lost. She said she is still trying to cope emotionally with the loss of Pierre.
"I hear Pierre's name every time I open my phone, and my heart drops every time, every time," she said. "What are we gonna do, kill each other forever? Until there is no one here? Cuz that's what we're doing."
But Johnson is determined to use her tragedy to help other families who are still struggling everyday with gun violence. She said she is trying to connect with other teens in the area who might feel hopeless and she's reaching out to other victims who might feel alone.
And there is a warning from federal authorities about the tiny gun switch. It may be small in size but it carries a big punishment. If you're convicted of possessing a machine gun conversion device, the penalty is up to 10 years in federal prison and more than $10,000 in fines.