Updated 12/12/12 – 5:44 p.m.

CHICAGO (CBS) — The brother of murder victim has filed a lawsuit against a website that allegedly helped the killer obtain the murder weapon.

CBS 2’s Dana Kozlov reports it’s the first lawsuit of its kind – aimed at stopping Internet gun brokers.

A stalker killed Jitka Vesel last year. Now her brother and the Brady Center to Prevent Gun violence are taking aim at armslist.com on her behalf, alleging the company failed to perform a background check on Dmitry Smirnov, who pleaded guilty to killing her.

“I’ll never meet anyone as unique and funny and joyful,” said Theresa O’Rourke, Vesel’s best friend since age 11.

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In April, 2011, Smirnov followed Vesel into the parking lot of an Oak Brook corporate park, after tracking her with a GPS device that was glued to her car.

He then shot her to death. Vesel was shot 12 times as she tried to run from Smirnov. They had only dated for a few weeks when she broke up with him 2 1/2 years before she was shot.

Smirnov admitted stalking and killing Vesel because she had broken up with him.

Now, O’Rourke is lending her voice to a lawsuit filed against armslist.com, the Internet broker who helped match Smirnov with the gun’s seller.

“It’s gonna help ease my pain, because I know maybe I can prevent someone else from feeling this,” O’Rourke said.

Attorneys with the Brady Center to Prevent Gun Violence filed the lawsuit on behalf of Vesel’s brother, Alex Vesely.

“It’s unimaginable loss,” Vesely said.

Brady Center attorney Jonathan Lowy said armslist.dot com matches gun sellers and buyers without any regard to who’s legally able to make the transaction.

“The complaint alleges that the website’s design facilitates illegal gun sales to unlawful gun buyers, with no background checks, and no questions asked,” Lowy said.

On its website, armslist has a disclaimer stating users must comply with all laws, adding armslist does not get directly involved transactions.

Lowy said that’s not good enough.

“A lawsuit like this can send a message,” he said.

Trying to find a number for, or reach any employees of armslist is almost impossible, so CBS 2 was not able to get in touch with anyone from the website for comment.

Smirnov was sentenced to life in prison for killing Vesel.