CHICAGO (WLS) -- Illegal guns get into the hands of offenders many ways in Chicago. Some weapons are stolen. Some are borrowed. Some are sold.
Once a gun is found at a crime scene, the works begins for one unit. It's a team that has had an extraordinarily busy couple of days.
"On the streets, this is referred to as a 'cop killer,'" said Officer Arnold Dixon. "Because this will pierce any armor that we wear on the streets right now in Chicago."
When a weapon is recovered in Chicago, it ends up with the Chicago Police Department's firearm investigation team. Officers allege Dana Melchor gave the newly purchased FN 5.7mm caliber pistol to convicted felon Anthony Williams. Both were charged on Thursday.
"It actually can go through the bulletproof vest of an officer. So, what you want that for in the City of Chicago, I don't know," said Officer Jacinta O'Driscoll.
The officers are well aware of the violence affecting civilians and officers.
"We know that these guns are out there. There are bigger ones than the ones that we seized yesterday that we know will do a lot more damage," said Officer Arnold Dixon.
Investigators trace recovered weapons to the owners, if possible. They say some of the newer illegal guns start as legal purchases.
"The gun stores are not doing anything wrong. The people are purchasing the weapons and they're saying that the weapons are for them. But they're not for them, they're for somebody in the gangs," O'Driscoll said.
"You have someone who is legal, you know, with a good history, a good background. And they made a bad decision," Dixon said.
They say that was the case with Trevon German. He was charged Tuesday with illegal transfer of firearms, purchasing and selling firearms with no valid FOID card. Investigators say he bought five guns and sold them. One was recovered from a 2015 shooting.
"It's sad that these guns are showing up the way they are showing up," O'Driscoll said.
"I hate seeing innocent people hurt by the use of these weapons, or by the use of reckless people. You got a lot of reckless people out here and they will do anything they have to do to get revenge and they will do anything they have to do to get away," Dixon said.
If you recognize Officer O'Driscoll, it may be because she shared with ABC7 last week that she needs a liver transplant. She is out of other options and she says there is much work to be done.
For more on O'Driscoll's search for an organ donor, click here.
Meet the team chasing down Chicago's illegal gun runners