Jonathan Hill had been running a little over four hours when he hit mile 25.5 of the Boston Marathon. Suddenly, race officials told him to stop because a set of explosions near the finish line.
Thoughts of muscle cramps and fatigue quickly turned into panic. His wife, Paulina, was at the finish line waiting for him, eight and a half months pregnant.
"I literally just started weeping and crying uncontrollably. All I could think about was the worst," Hill told The Huffington Post. "You're just drained, and your emotions take over."
Hill was among the many runners nearing their mental and physical limits Monday afternoon when chaos struck after two explosive devices killed at least 3 people and wounded more than 170.
Does that kind of exertion add yet another layer of physical and emotional trauma or does it obscure some of the pain? Experts say it's a complicated question.
It remains unclear how many of those injured during the explosions are runners vs. spectators, but as The New York Times noted, almost three-quarters of the 23,000 people who raced had already crossed the Boston Marathon finish line when the explosions went off.
From a physical perspective at least, Dr. John Vasudevan, who specializes in sports medicine at Penn Medicine, noted that vital organs are taxed immediately following an endurance race. Research shows that right after a marathon, runners can exhibit signs of temporary injury to their kidneys, and mild cardiac disease, among other things.
"Running through a marathon, it puts your body into a minor form of shock," Vasudevan said. "You're already dehydrated, your electrolytes might already be off, you're already pushing a lot of your vital organs to their limit. You sustain something even greater, that can be the straw that breaks the camel's back."
On the other hand, Vasudevan notes, any runners who sustained injuries would have had the advantage of being in peak physical condition on race day, making their bodies better equipped to endure trauma or surgery.
"Those who can train for and complete a marathon generally have a great reserve to recover from the stresses that they put their body through," Vasudevan said. "Their muscles have been trained to soak up a lot of nutrients. Their lungs have been trained to extract a lot of oxygen from the air. Their heart is already capable of distributing blood and nutrition throughout the system in a way that the average person is not."
The psychological picture that could emerge from enduring a trauma during a state of near-exhaustion is also complex.
"I think the timing was aimed for maximum psychological impact, in part, because people are physiologically exhausted," said Dr. Drew Ramsey, an assistant professor of clinical psychiatry at Columbia University.
Ramsey also noted the significance of the bomb's trajectory among a group of runners and spectators.
"Literally, right at the finish line after months of training, and four hours of extreme effort, you then have the finish line literally taken away from you," Ramsey said.
Still, David Yusko, a clinical psychologist who specializes in trauma and post-traumatic stress disorder at Penn Medicine, said stories from Monday's tragedy are likely to show both sides: There will be people for whom the hours of running made things worse, and others for whom it was a factor in protecting them.
"I think what you typically see is that during the moment, people kind of do what they need to do in order to kind of cope with the situation at hand. And they actually do it quite successfully because of the rush of the adrenaline and things like cortisol," Yusko said. "That fight-or-flight response is very adaptive and it just functions really well."
Indeed, some runners somehow had the ability to tend to the wounded, and others continued racing to the hospital to donate blood.
Still, Yusko said the most important thing following a tragedy like the Boston Marathon bombings -- emotionally at least -- is how people take care of themselves afterwards, and what kind of support networks they have.
Hill, for his part, spent the day with his wife, thankful for a muscle cramp that came somewhere around mile 21. He had to slow down, so Paulina had not yet crossed the street from the spectating stands to the area directly in front of the explosion, where officials had told her it would be easier to greet her husband.
"I just keep playing back in my mind, if I had a been a little bit faster, things could have been drastically different," Hill said. "We just left church a few minutes ago. We keep just looking at each other, and holding each other."