According to Spanish press, Francisco José Garzón Amo made a panicked call to the rail authorities ahead of the bend that prompted the crash. "I'm going at 190km/h," he apparently told them, sounding desperate. "I'm going to derail."
Garzón Amo was right: the train broke free of the rail and went flying, ripping doors from their frames. 80 passengers were killed, and dozens of victims are still in hospital. One American was amongst the dead.
After he'd discovered the extent of the crash, Garzón Amo reportedly said, "I messed up. I want to die. So many people dead, so many people dead."
But investigators are warning that the cause of the crash was likely more complex than speeding. Experts have noted that the train's safety systems should have kicked in and braked; the train was sophisticated enough that it shouldn't have derailed just because it was going fast. They've ruled out foul play: "We are moving away from the hypothesis of sabotage or attack," said one official.
"I'm coming from hell,' firefighter Jaime Tizon told Spanish paper ABC, after he'd dragged bodies from the site. "I couldn't tell you if the engine was on fire, or one of the carriages, or what...'
CCTV footage captured the accident, but it's a disturbing watch.
Driver Garzón Amo had worked for Renfe, the train's parent company, for 30 years. In March 2012, he posted a photo on Facebook of the train's speedometer, writing:
I'm at the limit and I can't go any faster or they will give me a fine... What a blast it would be to go parallel with the Guardia Civil [Spanish police] and go past them triggering the radar. Haha what a fine for Renfe haha.
He's now in hospital under police watch. It's expected that he'll be interviewed today.
The crash occurred close to Santiago de Compostela, a capital city in northwestern Spain. Spanish Prime Minister Mariano Rajoy, for whom Santiago is home, has declared three days of national mourning.
"Today is a very difficult day," Rajoy said. "This is the saddest Day of St James of my life." He referred to the capital's annual festivities, set to take place on Thursday, which were cancelled.
Earlier, Rajoy had sent a message of condolence e-mail to citizens of the region — which, it turns out, was exactly the same as a mass e-mail he sent earlier this week to China's earthquake victims.