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Tucson man faces federal charges after supplying part of AR-15 used to ambush & kill Pima constable, 2 others

Tucson man faces federal charges after supplying part of AR-15 used to ambush & kill Pima constable, 2 others

Josue Lopez Quintana allegedly bought 'lower receiver' for weapon & lied to federal agents about purchase

  • A guard of honor prepares to transport the body of slain Constable Deborah Martinez from the scene on Thursday evening.
    Paul Ingram/TucsonSentinel.comA guard of honor prepares to transport the body of slain Constable Deborah Martinez from the scene on Thursday evening.

Federal agents arrested a Tucson man after they linked him to the purchase of a gun part used in the AR-15 rifle used to ambush and kill Pima County Constable Deborah Martinez and two others at a North Side apartment complex last month.

Four weeks ago, Gavin Lee Stansell, 24, used an AR-15-style rifle to shoot and kill Martinez, Angela Fox-Heath and Elijah Miranda before he turned the gun on himself.

Josue Lopez Quintana, 25, was indicted on Sept. 15, and charged with lying to federal agents and falsely filling out a federal form. Last November, Lopez-Quintana purchased the lower receiver for an AR-15-style rifle, and later sold the part to Stansell.

Lopez-Quintana appeared in court on Monday, but the case remained undisclosed until Thursday when U.S. District Judge Eric J. Markovich ordered the case unsealed.

Lopez-Quintana faces up to 5 years in prison and a $250,000 fine.

On Aug. 25, Stansell used a Sharps Bros MFG model Livewire 5.56mm rifle to ambush and kill Martinez, along with 28-year-old Angela Fox-Heath as they attempted to serve him an eviction notice at Lind Commons apartments.

After killing both women, the gunman broke through the wall of a closet in his apartment and entered a neighbor's apartment, where he found 25-year-old Elijah Miranda, shooting and killing him. Miranda was staying in the neighboring apartment to escape from the summer heat. The resident of that apartment, who was not at home, had earlier been threatened by the shooter.

The gunman then killed himself.

According to court records, following the mass shooting, agents with the Bureau of Alcohol, Tobacco, Firearms and Explosives linked the weapon used by Stansell to Lopez-Quintana, tracing the serial number on the rifle's lower receiver. The lower receiver houses internal components, including the firing mechanism, and is what federal officials classify as the firearm for the AR-15-style semi-automatic rifles. Because this part is integral to making the firearm, it is controlled more strictly than other AR-15 parts, and purchasing one requires filing out a federal form.

When Lopez-Quintana bought the part, he filled out a federal form, known as a ATF Form 4473 and wrote he was "the actual buyer" of the lower receiver. On Aug. 26, ATF agents along with special agents with Homeland Security Investigations, a part of U.S. Immigration and Customs Enforcement, interviewed Lopez-Quintana. During the interview, Lopez-Quintana allegedly lied and told the agents he bought the lower receiver to "build an 'AR' for himself." He also said he later sold the lower receiver to "his friend 'Gavin' in 'April or May,'" according to complaint.

Agents reviewed his cellphone records, and found that Stansell asked Lopez-Quintana to buy the part for him online in November. Lopez-Quintana bought the lower receiver for him and had it delivered to a gun dealer in Tucson. Lopez-Quintana told agents that Stansell explained he needed help because he had an out-of-state identification card. After the purchase, Stansell payed Lopez-Quintana back.

On Aug. 30, Lopez-Quintana told agents he "lied to them to minimize his involvement."

Stansell had been trying to 3-D print his own gun parts, sources told the Sentinel.

Incident unfolds

On Thursday, Aug. 25 dispatchers received a call around 11:13 a.m. that shots had been fired at at Lind Commons, an apartment complex in the 3400 block of East Lind Road, said Sgt. Richard Gradillas, a spokesman for Tucson Police Department

TPD officers arrived and found Fox-Heath dead in the courtyard with "obvious signs of gunshot trauma," he said.

Gradillas said police believe Stansell opened fire as Martinez and Fox-Heath went to contact him, fatally wounding Fox-Heath. Martinez was found inside the apartment by members of TPD's SWAT team, who arrived after police realized they couldn't find the constable and believed she was inside the apartment with the gunman.

During the incident, residents at the apartment complex were evacuated from their homes, and placed in Sun Tran bus just a few blocks away.

Police entered the apartment and found Martinez inside, dead from gunshot wounds. Officers later found the shooter dead in his apartment, and Miranda dead in the apartment next door.

Court records show that an eviction order was to be served on Stansell. A hearing in that case was held the Monday before the incident, with the order issued the next day, Pima County Justice Court records showed. According to a court filing by the landlord's attorney, Stansell had threatened another resident of the apartment complex with a gun.

Local online court records showed no prior criminal offenses by Stansell, but he has a more lengthy criminal record in Hawaii.

The complex, previously known as Palo Verde Terrace, has been the scene of previous violent incidents, including a January 2022 drug-related shooting that left a man hospitalized. Seventeen 9mm bullet casings were found at the scene of that incident. And, sources have told the Sentinel that the apartment complex has been the site of at least several overdose deaths in recent years.

Following the shooting,  more than a dozen local law enforcement officers were at the apartments, and the SWAT team had been called out earlier, with about 100 officers initially responding. TPD officers were not involved in the incident while shooting took place, Gradillas said, but responded to a "shots fired" call.

Martinez was appointed as a constable, responsible for serving court papers such as evictions and orders of protection, in March 2022, filling a vacancy left by the resignation of Constable Kristen Randall. Martinez was seeking to continue in her post by being elected in her Midtown precinct, despite being under investigation by the Arizona Constable Ethics, Standards and Training Board for allegations of potential felony fraud, forgery, perjury and tampering with public records.

A Tucson native and Pueblo High School graduate, Martinez retired from U.S. Army intelligence after multiple tours in Afghanistan and serving for 16 years.

Martinez is survived by her husband, Gabriel Garibay, and 22-year-old daughter Ryane Martinez. On Sept. 1, a Catholic mass was held in Martinez's honor at St. Augustine Cathedral in downtown Tucson.

The investigation against Lopez-Quintana is being conducted by the ATF, with help from TPD and HSI. The Financial Crimes and Public Corruption Section of the U.S. Attorney’s Office, District of Arizona, Tucson, is handling the prosecution, said Yvette Cantu, a Justice Department spokeswoman.

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