The Arapahoe County Fairgrounds will fill with runners, police dogs, and their handlers on August 29 for the 5th annual RexRun for PAWSitivity, a family fundraiser built around a Sheriff's Office dog who has become something of a local legend. The event runs from 7:00 a.m. to noon and features a 5K run/walk, a 1-mile fun run, police K9 demonstrations, and a costume contest for dogs, all in support of a nonprofit that keeps local K9 units equipped and cared for.
The race is named for K9 Rex, who, according to the Arapahoe County Sheriff's Office, works alongside Deputy John Gray providing comfort, smiles, and support to students every day. Rex was sworn in as the Arapahoe County Sheriff's Office's first dedicated school therapy dog and is assigned to Deputy Gray at Thunder Ridge Middle School in Aurora, where he also serves classrooms across Littleton Public Schools to help students dealing with trauma or mental health crises, according to BetterUnite.
Rex's role has expanded well beyond comfort visits. In April, he completed his first successful live search-and-rescue track, locating a missing 7-year-old girl in a backyard within 12 minutes after picking up her scent from her shoes, according to RedState. The mission unfolded in an Arapahoe County neighborhood after the girl had been separated from her family for nearly two hours. Rex is also cross-trained in firearms evidence detection; a Facebook video posted in April documented him locating three spent shell casings hidden in a rock bed during an active shooting investigation, after detectives requested his help when manual searches had turned up nothing.
A Nonprofit Filling the Budget Gap
RexRun benefits Back The Blue K-9 Force, a nonprofit 501(c)(3) volunteer organization that puts 100 percent of net proceeds toward equipment, training, and care for hardworking K9s, per the seed facts behind Saturday's announcement. The group traces back to March 2016, when local volunteers in Centennial raised funds in just six weeks to buy lightweight ballistic vests for four Arapahoe County Sheriff's Office dogs and two Greenwood Village Police Department K-9s, according to the organization's own account on RunSignup. That effort started after community members learned the department's standard vests were heavy and ill-fitting.
Over the following decade, the all-volunteer group has funded the acquisition of 17 K-9s for five Colorado law enforcement agencies, along with specialized body armor, training gear, and emergency veterinary care. Race organizers cite National Police Dog Foundation data showing that more than 80 percent of police department budgets go to salaries, leaving little room for line items like K-9 purchases, ballistic vests, or vehicle heat alarms — expenses that often fall to nonprofits like Back The Blue K-9 Force to cover.
From One Event to a Multi-Dog, Multi-District Program
The first RexRun for PAWSitivity was held on August 6, 2022, at Dove Valley Regional Park in Centennial, raising $33,000 for police K-9 and school therapy dog programs, according to Colorado Community Media's coverage at the time. That inaugural gathering brought together law enforcement agencies, community members, and therapy horses. The program has since grown to support a multi-dog team across three Colorado school districts, including Rex along with dogs named Riley, Zeke, Bear, and Otis, all dual-certified in therapy support and detection work, per RunSignup's race page.
This year's schedule at the Arapahoe County Fairgrounds kicks off with the National Anthem at 7:50 a.m., followed by the 5K trail run at 8:00 a.m., the 5K walk at 8:10 a.m., and a 1-mile kids run at 8:45 a.m. Registered runners get a free flapjack breakfast from the Flippin' Flapjacks food truck, and the grounds will also host an interactive Kids Zone and vendor marketplace, face painting, bounce houses, games and prizes, and live and silent auctions.
A Chance to Deputize Your Own Dog
Beyond the race itself, attendees can enroll their personal pets in an honorary swearing-in ceremony, complete with a badge and certificate signed by Arapahoe County Sheriff Tyler Brown and K9 Rex for one year of honorary service, according to Endurance Grid's event listing. Dogs must stay on a 6-foot leash throughout the fairgrounds. Organizers also promise a meeting with R2-D2 from Star Wars as part of the day's family activities.
The event is open to all ages and dogs and is described by organizers as a family-focused event supporting police K9s and school therapy dogs. Participating community organizations include Arapahoe County government, the City of Centennial government, the Arapahoe Mounted Unit, the Town of Bennett, and the Arapahoe County Fair & Event Center. Registration for the August 29 event is available at rexrun.com.
