It began with Psychedelicat, a horse that would have remained unremarkable for the rest of his life, were it not for the precise timing of his death. Of the 17 races the four-year-old had run, he’d won two—which is probably why, at Santa Anita Park in Arcadia, California, he was entered in a claiming race: Anyone could purchase him for $16,000 before the competition began. In an industry where a few elite racehorses go for tens of millions, mediocre thoroughbreds like Psychedelicat cost less than some children’s lesson horses.

Not even halfway into the race, his Kentucky Derby-winning jockey, Mario Gutierrez, felt something wrong in the horse’s gait and pulled Psychedelicat to a halt. The equine ambulance zipped onto the track, loaded the limping horse, and drove off. As it turned out, Psychedelicat had broken his sesamoid, a small, difficult-to-treat bone. He was euthanized.

A breakdown can be the result of a single bad step, but it’s most often a result of cumulative stress. The athlete—equine or human—overexerts themselves over time until, mid-game, a tendon snaps, a bone cracks. Slowly, and then all at once.

While injuries requiring that a horse be put down are not unusual among racehorses—most tracks can expect to see a few dozen a year—no one foresaw that Psychedelicat’s accident on December 30, 2018, would kick off a slew of deaths: In all, 30 horses would die at Santa Anita in a six-month span. Whether injured during workouts or mid-race, most met their end the same way: A broken bone, an emergency crew rushing to their side, a shot of a heavy sedative followed by a lethal injection.

The numbers at Santa Anita weren’t actually that different from previous years. In 2018, 37 horses died there. In 2017 and 2016? Fifty-four and 57, respectively. And, among tracks nationwide, Santa Anita wasn’t even the worst offender. Kentucky’s Churchill Downs and the Chicago-area Hawthorne tracks both had higher fatality rates than Santa Anita in 2018.

Over the decades, spates of racehorse deaths have shaken the industry. Sometimes the spikes are caused by track mismanagement or shoddy horsemanship, other times by bad luck. Few racing fans can forget the horror of some of the sport’s highest-profile breakdowns, such as when Barbaro, the beloved 2006 Kentucky Derby winner, shattered his hind leg in three places during the Preakness Stakes.

This time, though, people started paying attention in a different way. Media swarmed to the story and protestors called for the track to be closed or for racing to even be banned in California altogether. One particularly damning Deadspin headline in early April: “They Killed Yet Another Horse at Santa Anita.”

“I think this is a crisis that’s been brewing for some time, and we really didn’t acknowledge it,” says Eoin Harty, a longtime horse trainer and head of the California Thoroughbred Trainers association. Now, ignoring it became impossible.

What was going wrong? More importantly, was there any way to put a stop it?

Talk to a dozen different horse people and you’ll get a dozen different opinions about why horses break down. Racehorses are bred for careers that burn fast and bright, rather than for longevity. The unknown side effects of increasingly popular medicines (such as bisphosphonates, which prevent bone loss when used correctly but are overprescribed and may interfere with the normal reknitting of bones) or medical procedures (such as shock-wave therapy, which is supposed to reduce inflammation and trigger healing in tissue but also causes numbing). Trainers who may not give their horses the right balance of rest to work. Whips, which encourage horses to run faster and faster, even when they may be in pain. The construction of modern thoroughbreds, thousand-pound athletes on toothpick legs. The format of races in which purse money may be more valuable than the horses running. When it comes to the last year at Santa Anita in particular, they may blame a perfect storm of events—or the literal winter storms—that befell the track.