Anna Thallas speaks to reporters about a bill requiring people to report lost and stolen guns. (Jesse Paul, The Colorado Sun)

The family of a woman fatally shot last year in Denver has filed a wrongful death lawsuit against the alleged shooter and the former police sergeant whose gun police believe was used in the shooting.

Attorneys for Isabella Thallas’ father, Joshua Thallas, and her boyfriend, Darian Simon, filed the lawsuit in Denver District Court on Tuesday, The Denver Post reported. Simon was also shot, but survived.

Simon’s attorney, Craig Silverman, said he and the Thallas family filed the lawsuit to learn more about how the shooting happened, including the relationship between the former Denver Police Department sergeant and the suspected shooter and how the suspect retrieved the ex-sergeant’s AK-47.

Silverman is a Colorado Sun guest opinion writer.

The lawsuit alleges former Sgt. Dan Politica, who retired in March, failed to securely store the rifle in his home, which allowed the suspected shooter, Michael Close, to take it.

Prosecutors said Close shot Isabella Thallas, 21, and Simon on June 10 while the couple were walking their dog. Close has pleaded not guilty by reason of insanity to multiple charges in connection to the shooting.

Silverman said he still wants to know why Close wasn’t charged with stealing the weapon and why the gun was not reported stolen until more than a week after the shooting.

“We have been told scant information about the relationship between Politica and the murderer other than they were friends and confidants and grew up together in metro Denver,” Silverman said. “We want to know why the murderer was in possession of this weapon, which was outlawed in Denver. We also want to know how he obtained the ammunition and the large-capacity magazines that are outlawed in Colorado.”

A transcript of court testimony in November by Denver Police Detective Joseph Trujillo, who is investigating the shooting, revealed Close and Politica have been friends for two decades. Investigators also said Politicia reported being concerned about Close’s mental health.

Trujillo testified that Close had left a voicemail on Politica’s phone minutes before the shooting saying he had “done something really bad” and “there’s no going back from this now.”

Close remains in custody. Politica’s attorney, Reid Elkus, on Tuesday declined to comment about the shooting.

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