A woman was fatally shot while walking a dog. The suspects gun was a police officers AK-47.

The man in the ground-level apartment asked the couple if they were going to train the dog or just command the pet to "go poop," according to a probable cause statement. Simon ignored the man until he saw him point what Simon believed to be a pellet gun at him and his girlfriend, Isabella Thallas.

But instead of a toy gun, it was an AK-47 and multiple shots rang out from the apartment, police said. Thallas, 21, was killed and Simon was injured in a random shooting that rocked the city. The shooting suspect, Michael Close, 36, faces multiple charges, including first-degree murder, and has pleaded not guilty by reason of insanity.

Nearly a year later, there's another wrinkle: The rifle allegedly used to kill Thallas and injure Simon was a personal firearm of a Denver police officer who was a longtime friend of the suspect. The details of who owned the gun involved in the shooting, first reported by KUSA earlier this year, were later confirmed by the Denver Police Department.

Dan Politica, who was a Denver police sergeant, reportedly resigned from the force in March, local media reported this week. Police had previously said that the gun was taken from Politica by Close, a friend of his for roughly 20 years, without his permission, and that the officer had informed the department that the rifle had been missing, reported the Denver Post. In a letter with the subject line, "Letter of resignation," that was obtained by The Washington Post, Politica did not offer a reason for his exit.

Politica does not face charges related to the shooting and had no open internal investigations at the time he left the department, his attorney, Reid Elkus, told The Post. Elkus said that the sergeant did not resign from the department but retired. "He absolutely was not forced into retirement," said Elkus, adding that Politica received a retirement party and plaque and is receiving his full pension benefits. He had been with the Denver Police Department since 2005.

News of Politica's departure has unfolded as the state continues to grapple with what to do about assault-style weapons that have shattered Colorado in mass shootings in recent years. While the state has passed legislation to help prevent gun violence, the push to ban assault-style weapons in Colorado remains difficult for lawmakers.

The city of Denver has had a ban on assault weapons for years that the state Supreme Court ruled in 2006 was allowed to stand. The details of how Politica acquired the weapon and where it was stored remain unclear, and his attorney declined to comment on the matter. Craig Silverman, an attorney representing Simon, said to The Post that Close allegedly fired 24 shots.

One of the Colorado bills signed into law was named after Thallas, who had celebrated her 21st birthday two days before her death on June 10, 2020. The bill signed into law last month by Colorado Democratic Gov. Jared Polis creates penalties for those in the state who fail to report lost or stolen firearms. He was joined by Thallas's mother, Ana, who fought back tears wondering why it took her daughter's death to help bring change.

"What saddens me, and what hurts the most, is that it takes a mother of murdered daughter to stand up and speak and try to make a difference in this state," the mother said at a news conference last month.

Neither the Denver Police Department nor Josh Maximon, an attorney retained by Thallas's father, immediately returned requests for comment.

It was a late Wednesday morning when the couple took Simon's dog, Rocco, out for a walk in the Ballpark neighborhood of downtown Denver, according to court documents of a preliminary hearing. The dog had been unable to go to the bathroom for a couple days and the couple was concerned.

Around the time Close started yelling at the couple, he allegedly texted Politica around 11:30 a.m. about how his dog had been recently attacked by other pets and how he was going to murder someone, according to court testimony from Denver Police Detective Joseph Trujillo, the investigating officer. Trujillo, who testified that Close and Politica had been friends for almost two decades, noted that the officer was concerned for his friend's mental health.

Simon, co-founder of the fashion company and brand Be A Good Person, was taken to the hospital with two nonfatal gunshot wounds to his leg, Silverman said. Thallas was pronounced dead at the scene, and her autopsy concluded she died of a gunshot wound.

After the shooting, Close allegedly left a voice mail for Politica at 11:40 a.m. about how he had "done something really bad."

"There's no going back from this now," Close said, according to Trujillo's testimony.

When the Park County Sheriff's Office arrested Close about an hour later, they found him in his car near Pine Junction, Colo., with a rifle and a handgun as well as a gun belt and multiple magazines of ammunition, according to an arrest affidavit. Close did not have any previous arrests in Colorado, according to the Denver Post.

Aside from the first-degree murder charge, Close also faces charges of attempted murder, use of a prohibited large-capacity magazine during a crime and assault. A judge ordered that Close be held without bond.

Thallas's mother recalled to KDVR that she only learned of her daughter's fate when she found out that Simon was at the hospital but her child was not.

"Then her sister texted me something from the news. A shooting in the ballpark area, one in surgery and one dead. I saw that and I knew. I felt it. I just fell, I couldn't breathe," she told the outlet. "It was like somebody had kicked me in my stomach."

As the city mourned the loss of Thallas through vigils and a mural, her death sparked questions as to how this young woman went to walk her boyfriend's dog and ended up dead. The detail of the AK-47 belonging to Politica was first publicly brought to light in a Facebook post from Thallas's mother in January, reported KUSA, in which she claimed that her daughter was "murdered with an AK-47 that belonged to a Denver Police Sergeant." The police department acknowledged to the TV station that the rifle was not issued by authorities.

Years before the fatal incident involving his firearm, Politica was suspended for harassing a street performer and starting a brawl that resulted in false arrests in 2016.

But Politica's resignation has brought even more questions and doubt for the family of Thallas, who was remembered by her father on Silverman's podcast as having a big heart and wanting to get into the fashion industry. Joshua Thallas, her father, wondered to KDVR why Politica was leaving the force now: "If there was no wrongdoing, why should he leave his job?"

"We're just looking for an answer. It's been almost a year, we've played by the rules, we've stayed quiet when asked to be quiet by the DA, and attorneys, and it's time to have a voice," he said. "It's time to know why. Not just us as a family and friends. Everybody wants to know what the heck has gone on."