He finally returned to his Michigan hometown this week - six months after the explosion that cost him his arms and legs - to serve as the grand marshal of his old high school's homecoming parade.
"I didn't come to Vassar yet, because I wasn't ready for people to see me without my legs. ... Because in Vassar, everybody knows everybody," Mills said in an interview hours before the parade Thursday. "Great town, but I just wasn't comfortable with them seeing me in a wheelchair."
Mills is still undergoing rehabilitation at Walter Reed Medical Center in Washington, D.C. But he's been able to get out and about. In the past few weeks alone, he took part in a 5K benefit walk in New York and celebrated his daughter's first birthday on the base at Fort Bragg, N.C.
His hometown has pulled for him from afar. Hair salons, American Legion posts and many others hosted fundraisers this spring and summer as the small, tight-knit community rallied around him.
Hundreds of people waving American flags jammed into Vassar's downtown to catch a glimpse of Mills at the parade Thursday evening. Mills, his wife, Kelsey, and their 1-year-old daughter, Chloe, served as the grand marshals.
Mills stood tall in the back of a Jeep, smiling and waving his left prosthetic arm as people screamed his name. He occasionally yelled out the name of someone he recognized.
Mills barely suffered a scratch during his first two tours of Afghanistan, but during his third, on April 10, he placed a bag of ammunition down on an improvised explosive device. The resulting blast tore through the athlete's muscular 6-foot-3 frame. Since then, he's undergone a grueling series of medical procedures and been pushed to the limits by medical professionals intent on seeing him pull through his rare injury.
A half a year since Mills' life was changed forever, it's difficult to find a tree, lamppost or telephone pole without a yellow or red, white and blue ribbon in this bucolic community of 2,700 that sits 90 miles north of Detroit.
A downtown bank proudly displays an electronic sign that welcomes Mills as a "hometown hero," as do dozens of other businesses.
"It was a lot to take in," Mills said of the signs of support he saw on the drive from the airport to his parents' home. "Now, I just have to make sure not to let everyone down."
At a bonfire after Thursday's parade, Mills those gathered that that his "family was really touched" by the love they've received. "Coming into town was amazing," he said.
Paul Wojno, Vassar High's principal, said the turnout for the parade and bonfire was "nothing short of fantastic," noting organizers handed out 1,500 flags and not everyone along the route had one.
Mills also plans to address the crowd before Friday night's Vassar High football game.
The 25-year-old is one of only a few servicemen to lose all four limbs in combat during the Iraq and Afghanistan wars and survive.
"This is my new normal, and it's all about how I adjust to it," he said moments after using his prosthetic legs to walk from the living room to the sun room at his childhood home. "There's no good that's gonna come from me sitting there and wondering, 'Why'd this happen? Why me? Now what do I do?' The answer's right in front of you: It happened because it happened."
Mills almost didn't come home at all.
Within 20 seconds of the IED explosion, a fast-working medic affixed tourniquets to all four of Mills' limbs to ensure he wouldn't bleed to death.
The medic was able to save Mills' life but not his limbs.
In the days since, Mills has worked out daily at Walter Reed, getting used to the prosthetics, but also strengthening his body for the rigors of what's to come once he leaves.
Mills was told quadruple amputees require at least 2½ years of recovery and rehabilitation. But his goal is to be out of Walter Reed and back home in less than half that.
"I am going to be out of here" in a year, he boldly told his doctor.
After that, he isn't sure what the future holds. He might go back to school, or perhaps work as an instructor at Fort Bragg.
Before any of that, however, he said he's looking forward to spending an "emotional" two days with hundreds of his closest friends in Vassar.