CHICAGO (CBS) — A lawsuit Wednesday accused an online gun marketplace of complicity in the shooting that killed Chicago Police Cmdr. Paul Bauer two years ago.

The lawsuit was filed in U.S. District Court in the Eastern District of Wisconsin Wednesday by Bauer’s widow, Erin Bauer. It named Armslist and those who run the online marketplace – Brian Mancini, Jonathan Gibbon, and Broc Elmore.

The Glock 26 9mm handgun used in the Feb. 13, 2018 shooting was sold through Armslist, the lawsuit said.

The lawsuit accused Armslist and its leaders of encouraging and profiting from illegal firearms sales. Marketplaces such as Armslist are often used by people who are not allowed to buy guns, and gun traffickers, because purchasers are enabled to get around any need for a background check, the lawsuit said.

People have used Armslist to set up illicit and unlicensed online gun “stores,” a fact that the lawsuit called a foreseeable consequence of the fact that Armslist chooses not to use “features, policies and content designed to minimize the risk of illegal transactions which supply the criminal market.”

One of those virtual gun stores was being operated on Armslist by Thomas Caldwell of Wisconsin – who later pleaded guilty to selling firearms without a license and was sentenced to three years and one month in prison.

A gun trafficker from the Milwaukee area – identified in the lawsuit as Ron Jones – found Caldwell’s store and bought weapons without any background check, the lawsuit said.

In 2017, Jones bought a Glock 26 9mm handgun that ended up on the broader criminal market, the lawsuit said. It ended up in the hands of Shomari Legghette – who was not allowed to buy guns legally because of past felony convictions.

Legghette is accused of shooting and killing Bauer outside of the Thompson Center downtown.

Authorities at the time said Legghette was carrying a semi-automatic handgun with a 30-round magazine, and was wearing body armor. He allegedly shot Bauer at least four times in the head. Sources say he also was carrying multiple bags of heroin, crack cocaine, and marijuana at the time he was arrested.

Bauer, who was commander of the Police Department’s Near North (18th) District, confronted Legghette at the Thompson Center around 2 p.m. on Tuesday after chasing him down Clark Street. Legghette was running from tactical officers who had stopped him for questioning near the Renaissance Hotel near State and Lake streets. Bauer heard about the pursuit on his police radio and was attempting to stop Legghette when he was shot.

Bauer and Legghette engaged in a struggle, and they fell down a flight of stairs at the Thompson Center. At that point, several shots, up to seven of them, were fired and Bauer was mortally wounded.

Legghette was arrested moments later as he tried to escape.

The lawsuit accused Armslist and its leaders of being negligent and “at minimum, responsible as knowing accomplices or co-conspirators for Caldwell’s violations of (the law).” It called for compensatory and punitive damages, as well as an order that those who run Armslist either change their business practices or be shut down.

Armslist has not commented on the lawsuit.