A Fort Stewart soldier who was killed in a wreck while bicycling Monday morning was a tireless advocate for wounded veterans who turned heads with a record-breaking run last year.

Sgt. 1st Class Augusto "Tito" Piñeiro was riding a touring hand cycle on Ga. 119 about 7 a.m. Monday when he was struck from behind by a Toyota Prius driven by a 30-year-old Bryan County woman.

Georgia State Patrol trooper Jamie Quinn says the woman stopped, stayed with Piñeiro and flagged down a passing car. The driver she alerted was an Army medic who called 911 and gave Piñeiro CPR until an ambulance got to the scene. Piñeiro, 38, was rushed to Winn Army Community Hospital on Fort Stewart, where he was pronounced dead.

Piñeiro, most recently a combat engineer with the 3rd Infantry Division's 2nd Brigade Combat Team, was a combat veteran who served four deployments. The Florida native was a multiple-Purple Heart recipient who was injured in several improvised explosive device blasts while on foot patrol in Afghanistan in 2012, he told the Savannah Morning News in an interview last year.

"I dealt firsthand with a lot of people dying in front of me," Piñeiro said in 2016. "It took a hard beating on my mind and my body after that last deployment."

His experiences led him to join Operation Enduring Warrior, a nonprofit that helps wounded and at-risk veterans adjust to life after combat through athletics and other programs. He learned about the program at Fort Bragg, N.C., where he had starting running to relieve stress.

He decided to help spread the word by signing up for the nonprofit's Masked Athlete Team, competing in marathons and other events while wearing a Special Operations-style gas mask. When the mask was on, Piñeiro went by "Unbreakable."

"A lot of people don't seek out help because they're scared of what their leadership will think of them," Piñeiro said. "Operation Enduring Warrior helped me fight those demons, and that's what I want people to know: They don't have to fight it alone."

In May of last year, Piñeiro broke a record when he ran 100 miles in a gas mask at the Knock on Wood 100 in Greenville, S.C. The soldier wore one of the oxygen-restricting devices for the entire 37-hour journey, stopping every lap of a 3.2-mile loop to swap out the photo he was carrying - each of a veteran who was either killed in action or in need of help.

He had no plans of stopping his awareness-raising efforts, he said, adding that he planned to begin training for a triathlon wearing the mask.

"It's on to the next adventure," Piñeiro said.

He was known to train for his adventures along Ga. 119 and Ga. 144, the wooded highways that lead into Fort Stewart. No charges have been filed in the wreck, and the investigation is ongoing. Quinn, the state trooper, said the State Patrol's Specialized Collision Reconstruction Team is now handling the investigation, and that it could take several months before the work concludes.

Piñeiro was in the Army for 15 years, and had been at Fort Stewart since 2015.

"The 3rd Infantry Division and the Fort Stewart community express our condolences to the family and friends of Sgt. 1st Class Piñeiro," said Kevin Larson, spokesman for the installation.

Piñeiro leaves behind a wife and three children, and condolences for the family were plentiful on social media Tuesday.

"You've been a part of so many people's triumphs and tragedies and always pushed them to be better," one friend wrote on Facebook. "Words do not do justice for the person you are."

Many lauded his military career and his resolve.

"He was one tough soldier, father, husband and son," another friend wrote.