A friend of the gunman who killed nine people outside a Dayton, Ohio, bar last week told authorities that he bought body armor and equipment for the attacker and helped him assemble the weapon used in the rampage, according to a court filing unsealed Monday.

These details were included in a criminal complaint charging the friend - Ethan Kollie, 24 - with two counts relating to his purchase and possession of firearms. Neither count relates to the shooting itself.

Benjamin Glassman, U.S. Attorney for the Southern District of Ohio, stressed that while the charges emerged from the investigation into the Dayton shooting, they included no suggestion that Kollie knowingly played a role in plotting the attack.

"Mr. Kollie does not stand accused of intentionally participating in the planning of that shooting," Glassman said at a news briefing. "We have no evidence of that. There's no allegation of that."

An attorney listed for Kollie in court filings did not immediately respond to a request for comment.

Jail records showed that Kollie was arrested Friday evening, the same day the criminal complaint was filed. Kollie was charged with possessing a firearm while being an unlawful user of a controlled substance and making a false statement regarding firearms. He could face up to 15 years in prison, Glassman said.

Authorities said Connor Betts, a 24-year-old with a history of violence against girlfriends and who had a "hit list" of people he hoped to target, had donned body armor and a mask before opening fire with an assault-style weapon in a Dayton nightlife area early Aug. 4.

Before police officers shot and killed him, Betts killed nine people, among them his 22-year-old sister.

The Dayton attack was the second mass shooting in a matter of hours. Not long beforehand, a gunman in El Paso, Texas, opened fire at a Walmart popular with people on both sides of the border with Mexico, killing 22 people and injuring dozens more. Police said the gunman in El Paso told them he was targeting Mexicans, and authorities have called the El Paso shooting domestic terrorism.

In Dayton, the FBI has said it was investigating the shooting after learning that Betts explored "specific violent ideologies." Officials have said they are seeking clarity on what could have motivated Betts.

Kollie and Betts were friends who had repeatedly done "hard drugs" together, Andrew Gragan, an FBI special agent, wrote in an affidavit included in the complaint.

Kollie told FBI agents that he bought the body armor, equipment for the gun and a 100-round double-drum magazine that Betts later used during the massacre, Gragan wrote. He bought these items and stored them in his house "to assist Betts in hiding them from Betts' parents," Gragan continued.

While speaking to the FBI, Kollie also said that about 10 weeks before the shooting, he was in his apartment, watching and helping Betts assemble the weapon later used in the shooting. Weeks later, Betts retrieved the gun, magazine and body armor, Gragan wrote.

Betts's family has said it was "shocked and devastated" by the shooting and pledged to cooperate with law enforcement.

The complaint also quotes Kollie as acknowledging both drug use and lying about it on a federal form to be able to purchase a gun.

Federal agents interviewed Kollie on the day of the shooting, where he told them that he bought the body armor and a firearm accessory for Betts earlier in the year, Gragan wrote. The agents smelled marijuana, saw devices for smoking marijuana and learned that Kollie possessed two guns, Gragan wrote.

Four days later, the FBI interviewed him again, asking about Betts and their drug use together, which occurred "four to five times a week during 2014 to 2015," Gragan wrote. Kollie also told agents that he has smoked marijuana every day for a decade, Gragan said.

That same day, Gragan added, FBI agents conducting a search warrant asked Kollie whether he had anything on him; he had a bag of marijuana and a revolver. Kollie also told agents that he grew and used hallucinogenic mushrooms, Gragan wrote.

A firearms transaction form filled out by Kollie showed that he checked "No" in response to a question asking whether he unlawfully used marijuana or any other drug, according to Gragan. When asked why he answered this way, Gragan wrote, Kollie admitted that he lied to be able to obtain the gun.

Even though neither of the counts relates directly to the Dayton shooting rampage, the charges are still the first to arise out of the investigation into the massacre.

Investigations into terrorist attacks and mass killings have led to essentially unrelated criminal cases in the past. After the 2015 terrorist attack in San Bernardino, Calif., officials arrested three people connected to the shooters and accused them of a marriage fraud conspiracy, something officials said they discovered during their investigation into the deadly attack.

In El Paso, the shooting suspect was arrested and has been charged with capital murder. Federal officials have said they are weighing federal hate crimes charges in that case.