In June 2021, Anderson Lee Aldrich walked out of the front door of a house in Colorado Springs with his hands in the air after a stand-off with police.
Authorities arrested him for felony menacing and first degree kidnapping after his mother alleged that he had threatened her with a homemade bomb and other weapons.
Seventeen months later, Mr Aldrich, 22, is in police custody on suspicion of killing five people at an LGBT+ nightclub called Club Q.
What's more, media reports suggest that the weapons wielded during the attack – a semi-automatic rifle and a handgun – were purchased legally.
That was despite various state laws designed to stop dangerous people from getting hold of such weapons.
"These laws were put on the books exactly to address the dangerous behaviors that are often precursors to larger violent events," Shannon Frattaroli, a professor at the Johns Hopkins Center for Gun Violence Solutions, told Reuters.
"Threatening to blow up your mother or the neighborhood most reasonable people would agree is a signal that some intervention is needed."
So how exactly did the alleged Colorado Springs gunman get his firearms?
Colorado has universal gun background checks
According to CNN, law enforcement sources say the suspect appears to have legally purchased both of the guns he brought to the club.
The owners of Club Q told The New York Times that the gunman was wearing military-style body armour and appeared to be carrying a rifle and six magazines of ammunition.
Colorado has various laws designed to stop dangerous people from getting hold of such weapons. Almost all firearm sales, including private transactions such as at gun shows, are subject to background checks conducted by the Colorado Bureau of Investigation (CBI).
Buyers are disqualified if they have been convicted of a felony crime, convicted of domestic violence, judged to be mentally unfit, dishonourably discharged from the armed forces, or given a restraining order for harassing, stalking, or threatening their child or partner.
They can also be disqualified if they are fugitives, drug addicts, undocumented immigrants, have renounced US citizenship, or if they are indicted for any felony.
Around 330,000 to 490,000 of these checks are conducted every year, but only around 2 per cent tend to result in denials. That rate climbed to 2.8 per cent in 2020, when gun sales across America surged during the coronavirus pandemic.
In theory, if the Colorado Springs suspect had been convicted or indicted in 2021, he might have been unable to buy or keep a gun.
Suspect never formally charged over bomb threat incident
The problem is that Mr Aldrich was never formally charged after the 2021 incident, according to local newspaper The Gazette.
"No formal charges were pursued in this case, which has since been sealed, according to the district attorney's office," said the newspaper in an editor's note attached to its original story about the bomb threats.
In fact, the newspaper says Mr Aldrich himself phoned one of its editors in August and asked them to remove the story.
"There is absolutely nothing there, the case was dropped, and I'm asking you either remove or update the story," Mr Aldrich reportedly said. "The entire case was dismissed."
Hence, even if Mr Aldrich had tried to buy guns after June 2021, his previous arrest probably would not have shown up in the background check system.
In Colorado, criminal charges can come substantially after a person is arrested. Even now, the shooting suspect has been jailed on an “arrest-only” charge, meaning prosecutors have not formally charged him yet.
We don't know why the 2021 case was dropped, nor why the records were sealed. But it does appear that Mr Aldrich's mother Laura Voepel made a Facebook post in July 2021 asking for recommendations for a lawyer.
"Does anyone know of a fantastic defense attorney?" she asked in a local women's group. "I ask this with a heavy heart but my family really needs some help at this time."
On Monday, the chief of police in Colorado Springs said Ms Voepel had not cooperated with the investigation into the Club Q shooting, though he would "welcome an interview with her at any time".
Local sheriffs oppose the state’s ‘red flag’ law
What about Colorado's "red flag" law, which came into effect in January 2020?
The law allows citizens and police officers to petition a judge for an "extreme risk protection order" (ERPO) against any gun owner they believe to pose an imminent danger to themselves or others.
When granted, these orders force the gun owner to surrender their weapons for 14 days, and can be extended in six month increments up to one year.
But the sheriff's department in El Paso county, where Mr Aldrich was arrested, has declared itself politically opposed to the law and refuses to let its officers petition for such orders except in special circumstances.
In 2019, it joined nearly 2,000 counties across the US in declaring itself a "Second Amendment Sanctuary", saying the red flag law "infringes upon the inalienable rights of law-abiding citizens".
"A member of the El Paso County Sheriff's Office will not petition for an ERPO unless exigent circumstances exist, and probable cause can be established that a crime is being or has been committed," sheriff Bill Elder said in 2020.
An investigation by KUSA News found that only 60 per cent of petitions are granted, dropping to 32 per cent when they were filed by citizens rather than police officers.
It also found that El Paso had the joint lowest approval rate of any Colorado county in 2020 and 2021, with only eight out of 39 petitions being granted.
Asked by The Associated Press what had happened after Mr Aldrich's arrest last year, the El Paso sheriff's office declined to say.
‘This should have put him on the radar’
Gun control advocates and experts on gun violence say Saturday's shooting exposes holes in Colorado's regulations.
"We need heroes beforehand – parents, co-workers, friends, who are seeing someone go down this path," said Colorado legislator Tom Sullivan, whose son was killed in the 2021 Aurora cinema shooting and who sponsored the red flag law. "This should have alerted them, put him on their radar."
University of Colorado professor Chris Knoepke said:"It's heartbreaking when you hear one of these stories, and you worry that an opportunity was missed to potentially do something about it,"
The state's Democratic governor Jared Polis told Colorado Public Radio that the red flag law wasn't being used often enough.
"I think it needs to be really evangelised more and talked about more," he said. "I think that while it has been used a couple hundred times, I think that not everybody knows that it's on the books.
"We also have very disparate records of utilising it from different county sheriffs... I think everybody should look at their practices and say, 'hey, if there's somebody that we feel is dangerous, [and] there's not enough to take them in and hold them on a criminal charge, can we at least remove access to their weapons?'
"There is a way to do that under Colorado law, and I want to make sure people are aware of that."
