Phoenix’s alleged serial shooter unwittingly sold his freedom for $90.

That’s how much Aaron Saucedo got for his handgun from a local pawn shop, The Daily Beast has learned. Police say that transaction led them to Saucedo, who used that gun to kill his mother’s boyfriend in 2015. The following year, police say Saucedo used at least one other gun to shoot 11 more people, killing nine of them. Seven of the fatal shootings were in a four-month span that terrorized Arizona’s largest city.

“The pawn shop was certainly part of the investigation and helped us locate one of the guns involved in this series,” Sgt. Jonathan Howard told The Daily Beast.

The transaction that cracked the case wide open was made around 6:30 p.m. on Sept. 1, 2015. That’s when the 23-year-old wandered into Mo Money Pawn, blocks away from where he lived, to sell his Hi-Point 9mm pistol.

“We paid $90 for it,” general manager Byron Vaughn told The Daily Beast, adding, “We paid cash.”

The pistol, which retails for $199 brand new, was believed to be used by Saucedo to gun down 61-year-old Raul Romero in front of his home on Aug. 16, 2015. Romero had been dating Saucedo’s mother, authorities confirmed. Sixteen days later, Saucedo sold the gun police say was used to kill Romero to the pawn shop.

On Jan. 1, 2016, cops say Saucedo killed 22-year-old Jesse Olivas, who like Romero, was shot and killed in front of his home.

The hits kept coming.

Saucedo allegedly was the triggerman in a pair of non-fatal shootings involving a 16-year-old male and a 21-year-old man that occurred at 11:30 p.m. on March 17 and 18, 2016, according to Phoenix PD’s timeline of the deadly shootings.

In April 2016, cops say Saucedo murdered Diego Verdugo-Sanchez and Krystal Annette. In June, Saucedo allegedly killed Horacio De Jesus Pena outside his home and killed 19-year-old Manuel Castro Garci. On June 12, around 3 a.m., police say Saucedo fatally fired at three people including 12-year-old Maleah Ellis. Her mother died three weeks later.

And just before he was arrested in April 2017, Saucedo allegedly fired into a car where a 24-year-old man and a 4-year-old boy were sitting. Neither was hit.

In September 2015, police arrested Leslie Allen Merritt for the shootings but a judge ordered the case against him dropped seven months later. Merritt had sold the same type of gun used in the shootings—a Hi-Point 9mm—to the Mo Money Pawn Shop. (Arizona Gov. Doug Ducey even proclaimed, “We got him!”) It was later discovered the gun had been locked up at the shop during the shootings, meaning Merritt could not have been the killer.

Ironically, the same type of gun and the same pawn shop connected to Merritt led cops to Saucedo.

“It’s, you know, fortunate that we did our job like we were supposed to,” Vaughn said. “And because of that the police department had the information which they proceeded to go off of.”

Phoenix Police Chief Jeri Williams said the department received more than 33,000 tips after offering a reward of $30,000 for information.

“We hope that our community will rest a little easier and that our officers will get a little more sleep [knowing] that our wheels of justice are finally in motion,” she told reporters during a press conference on Monday.

Before he allegedly became a serial killer, Saucedo was a bus driver. According to AZCentral, Saucedo was summonsed for running a red-light back in September 2015 while driving a public bus. A snapshot released by the City of Phoenix shows Saucedo apparently running the light, his eyes hidden behind a pair of neon sunglasses.

The accused was booked into a Maricopa County jail for one count of homicide, and on April 19, was held on a $750,000 bond.

Cops on Monday say Saucedo was rebooked and hit with “26 additional felony counts” that ultimately ended a long nightmare for the city. The charges include: eight additional homicide counts, three counts of attempted homicide, six counts of drive-by shooting and multiple other counts including discharging a firearm at a non-residential structure.

Pressed about items Saucedo pawned, Vaughn said he couldn’t detail those due to confidentiality rules.

“He did several transactions with us over the years,” Mo Money Pawn’s Vaughn noted. “The other times he was buying stuff from us.”

But when it comes the law, Vaughn said he plays by the books.

“We always ID, absolutely,” he said. “Doesn’t matter if I know him or not. If my mother came in here to do a transaction I would take ID from her.”

Vaughn said he has no mercy for Saucedo if he is indeed the Serial Street Shooter.

“I hope that if he is guilty he pays for it,” Vaughn said. “He destroyed a lot of peoples’ lives.”