Runners blur by near the start of the 40th running of the Marine Corps Marathon on Oct. 25, 2015. (Toni L. Sandys/The Washington Post)

An anonymous person logged on to a popular running message board last week to report a crime against fair play. The person had been searching for a name on a database of Marine Corps Marathon finishers and unwittingly came across something suspicious.

“I think I have found a serial cheater,” the message board user typed on LetsRun.com.

It was around that same time that race organizers were doing some authenticating of their own. On Oct. 25, more than 23,000 runners weaved through Washington and Northern Virginia, but when organizers combed through the times of the top finishers, the results of one man drew a bright red flag.

For 50 minutes late in the race, the 61-year-old experienced runner from Washington left no record of his progress, but he reappeared at some point and ran at least the final five to six miles.

“We don’t know where he was,” said Rick Nealis, the race director. “He was sitting on a park bench or going in the Air and Space Museum. He’s doing something for 50 minutes, but I know he’s not running the race.”

Gregory Price participating in the 40th Marine Corps Marathon on Sunday, Oct. 25, 2015. The Marine Corps Marathon has issued Gregory Price, 61, of Washington, D.C., a lifetime ban from all its events after questions arose about his race times, missed timing mats and highly suspect splits at the race, which he has run 13 times since 1998. (MarathonFoto)

Gregory Price finished second in his age group last month with a time of 3 hours 17 minutes 47 seconds. Nealis was so certain that Price cheated that this week he purged the result from the race logs and issued a rare lifetime ban.

“You won’t see him running in the Marine Corps Marathon again,” Nealis said Thursday.

In a brief telephone interview Friday afternoon, Price admitted to shortening his marathon route in recent years and said he never entered a race with the intention of cheating.

“I messed up. There’s no reason to do that,” he said. “There’s really nothing else to say. There’s not a good explanation. I apologize to all the other runners.”

Price said he called Nealis on Friday to offer an apology. He said he had been a runner for most of his adult life, but in recent years, as his body struggled to make it 26.2 miles, he still fancied himself a marathon runner.

“I feel bad,” he said. “There’s no great back story to it. It’s just wrong. I haven’t been feeling that well, didn’t do the proper training. Now, at the end of the day, what do I have? Nothing.”

Runners train for months for a marathon, and many suffer through several failed attempts before successfully completing the grueling race. To cheat in a marathon is considered one of the sport’s most egregious sins. Perhaps most famously, a runner named Rosie Ruiz was the top woman finisher in the 1980 Boston Marathon but later was stripped of her title when race officials ruled that she didn’t complete the entire course. More recently, runners Mike Rossi and Kip Litton have been subjected to intense Internet sleuthing and scrutiny over their marathon results.

“A lot of running is about integrity and being yourself,” said Jim Hage, a two-time Marine Corps Marathon winner and a member of the race’s Hall of Fame. “The cliche is that there are no shortcuts to a marathon, and to have someone manufacture a shortcut is surprising. . . . I suppose non-runners might think it’s sort of funny and a quirky thing. Runners might take more offense because we understand more what the sport’s about, and it ain’t about shortcuts.”

In the weeks following the Marine Corps Marathon each year, race officials usually begin scouring the database and scrutinizing times posted by the top finishers, often cross-checking split times with photos that are taken along the course.

“In this case, you click on the photo, yeah, looks like a runner — 61 years old, fit, healthy black male,” Nealis said. “But then you look at the times, and you see he’s missing two mats.”

Every five kilometers and at 13.1 miles, race officials position wide rubber timing mats that register when a chip embedded on each runner’s bib passes by. So a runner who finishes the race should have nine split times between the start and the finish. Price, though, was missing times from the 25-kilometer mark, near the Martin Luther King Jr. Memorial, and again at 30 kilometers, near the U.S. Botanic Garden.

But the mat at the 35-kilometer mark, not far from the Pentagon, showed that Price had resurfaced on the race course and, according to the clock, apparently had been running much faster than at any other point of the race. Jeff Gilliland, 51, crossed the finish line shortly after Price and said he had to run around Price, who was standing calmly at the finish.

“I do remember thinking it was kind of strange,” Gilliland said. “At that point, you’re pretty gassed if you’ve been running a marathon at that pace. . . . I just thought it was weird there was a guy standing there like he had just walked across the line.”

The race director explained the mats sometimes miss the chip, and it’s possible race officials would have believed the fishy finish had this been Price’s first transgression. Price, though, had competed in the Marine Corps Marathon 13 times since 1998, and his past five races in particular included suspicious results. He had competed in the race every year since 2011, and each time the mat failed to register him at the 25-kilometer and 30-kilometer marks.

“You’re telling me the chip doesn’t work in the same spot only for this guy? Every year?” Nealis said. “Either there’s some spaceship that’s beaming down something just on him or something is up.”

The race director said that from 2004 to 2009, Price also had recorded suspect results, missing a chip mat in four of the six races.

In typical years, race officials throw out 125 to 250 suspicious results. Nealis said they’re usually more casual runners chasing a bucket-list goal: either completing a marathon or qualifying for the Boston Marathon. It’s rare that officials catch a serial cheat. Nealis can remember just a couple of other cases and says he has issued just five lifetime bans and a handful of one-year suspensions. Perhaps most memorably, in 2005, about eight runners from a Toronto-based running group took a shortcut and shaved four miles off the marathon route, each earning temporary bans.

Race records indicate Price has completed — in one fashion or another — at least 20 marathons. Nealis believes Price has run 20 miles in his each of his most recent Marine Corps attempts but never the full 26.2.

The Marine Corps race doesn’t award prize money and is not among the nation’s most prestigious marathons. Nealis sees only one compelling reason for an experienced runner to cheat here: The race serves as a qualifier for the Boston Marathon. The Boston race only accepts runners who qualify with specific times in other marathons or who raise money for charity. Nealis calls the race the “holy grail of running.”

Price said he wasn’t particularly aware of his time while on the course and wasn’t specifically trying to sneak his way into the Boston Marathon, but by virtue of his 2014 Marine Corps finish, Price was entered in this year’s Boston Marathon in April. Nealis said he sent a letter this week to Boston race officials explaining the situation, and Price’s name no longer appears on a list of this year’s entrants. Boston Marathon records indicate that Price has completed the race four times since 2001.

“You never like to hear someone of being a cheater,” said Tom Grilk, executive director of the Boston Athletic Association since 2011. “It’s a situation that I don’t have any personal familiarity with, but there’s no one I respect more than Rick Nealis and all the people down there. So I have every confidence they were very careful and made the right choice.”

Nealis said Price’s recent results have been wiped from the Marine Corps record books, and he also was booted from the Marine Corps Marathon Runners Club, an honor for having completed five races. The third-place finisher in last month’s race, Wayne Lundy, has been elevated to second and David Wild to third. They both will be honored at a ceremony next month, along with the other top finishers in each age bracket.

Lundy, a 60-year-old College Park resident, said the ban was important for maintaining the sport’s values.

“I knew what my time was. [Price’s ban] doesn’t change my time. But I think it’s valid that he be banned,” Lundy said. “Running is personal improvement and personal integrity, and when someone does something like that, he cheated in the race. A lot of runners take it personally because the individual has violated something a runner may consider a sacred thing. This is something we all love doing, and you just took a dump on it.”

Magda Jean-Louis contributed to this report.