Jason Peacock was runner No. 5263 at his first Boston Marathon.
He crossed the finish line and celebrated, then went back to the hotel and was coming down the stairs to cheer on other finishers when he heard it.
"And I said, 'Let's keep going 'til we can't hear sirens any more,'" Jason Peacock recalled.
Sirens are a familiar sound to him. He's a Public Safety Officer in Highland Park, meaning he serves the city as a cop, firefighter, and paramedic.
In the days leading up to the marathon, Peacock had traded stories with Boston's finest.
"They had all told me I'm crazy for running marathons, but that they'd be there cheering me on," he recalled.
In the minutes that followed the bombings, Peacock watched in horror as they did what he does.
"When bad things happen, most people run away... we run to the fight," Peacock said.
Now he is running back to Boston.
"And this year, I'm going back for a purpose — not just to run a marathon for me," he said. "It's not about me; it's about the City of Boston, the first responders, and everyone who was there that year."
Peacock leaves for the 2014 Boston Marathon on Thursday, and he's sporting a new look: A wiry mustache, brown with a few grey strands.
"Actually I like it, I like the mustache. Every now and again my wife tells me to quit petting it, because I’ll pet it," he said, laughing and running his fingers over it.
He grew the 'stache to raise some cash.
"The mustache is a very traditional symbol of law enforcement," Peacock explained. "Especially in Boston. If you pull up old photos from the 1800s and 1900s, they all had mustaches. It's just a very traditional image."
"Over the past year, not much has been done for those guys and girls who were there on the front lines, serving and protecting," he added.
So, along with his chiropractor, Dr. Logan Sherman (an elite runner who was in Boston in 2013 and is going back in 2014), Peacock created the Staches for Boston PD campaign. They've worked with Luke's Locker locations across Texas to hold fundraising social runs this week.
All the money raised will go to the Boston Police Foundation, a private organization that buys equipment and pays for training, things the city itself cannot afford.
"Everyone is going to be wearing Boston colors and wearing mustaches... and Luke's is giving out the free mustaches," Peacock said. "So if you can't grow one, we'll give you one!"
Sherman has a full beard, and he's preparing to shave down to just a mustache before Monday's big race.
"I've never been just a mustache," he said, laughing. "I'm a little nervous."
Peacock's wife is making sure he shaves soon, too.
"It's being shaved [in Boston] is what I was told," Peacock said, laughing. "I asked if it would be Marathon Monday night, but she said, no, we can do it Tuesday morning, so it's not flying home. It'll be going down the drain in Boston, unfortunately."
But he vows it's his new tradition. Neither of these runners ever considered not returning to Boston.
"I don't know of anyone I've talked to that was there last year that's not going back," Peacock said. "They all want to go back. Not only are we runners, we're Americans. We're strong. We persevere through everything."
"Like 9/11 and any other tragedy in American history, we don't want to forget," he added.
"I think that shows the resiliency of runners and how tough we are as a group," Sherman said.