Sánchez started his Wednesday proclaiming reasons to be “optimistic” as Spain’s election neared. Hours later, he was standing at the scene of a high-speed rail crash, explaining why at least 68 people were dead.

The accident — Spain’s deadliest rail crash in over a decade and second major collision this year — is a brutal blow for the prime minister, who’s already facing a difficult election campaign. Polls show the conservative People’s Party leading with far-right Vox on the rise, and Wednesday’s events are likely to only increase scrutiny on Sánchez and his Socialist Party.

The Spanish leader tried to get out ahead of any attacks on Wednesday, vowing swift accountability from the crash site about 118 kilometers (73 miles) south of Madrid. And for the moment, all major political parties except Vox have suspended scheduled campaign events, as Sánchez declares three days of mourning.

But the detente won’t last. In a sign the accident will only further polarize Spain’s fraught political landscape, a union tied to Vox was already calling for demonstrations on Wednesday night in front of the Transportation Ministry in Madrid. And Vox leader Santiago Abascal was bashing Sánchez within hours of the crash, before the cause or death toll was known.

People’s Party leader Alberto Núñez Feijóo, the frontrunner to replace Sánchez, avoided explicit political attacks, merely calling for a government investigation and judicial inquiry “with full resources, and free from interference.”“I am not going to get into a discussion about political responsibilities right now,” Feijóo told journalists in Madrid.

“Today is not the day for that.”Still, the the PP’s official X account posted a message in bold black letters: “That’s enough.”

Meanwhile, Sánchez said a government commission for railway accidents will investigate the causes, with early signs pointing to human error, unlike the crash earlier this year, which killed more than 40 people. “It is not acceptable for a country like Spain to suffer two high-speed railway accidents in the same year,” Sánchez said. “We will take all necessary measures and act with total decisiveness to rebuild the confidence in our high-speed railway system and to guarantee the safety of our citizens.”

Wednesday’s collision appears to have come down a fatal communication blunder. At roughly 8:30 a.m., the railway’s automatic security system stopped working, according to Transportation Minister Óscar Puente.

All trains in the affected area were halted and a control center in Madrid took over, operated by state-owned railway infrastructure operator Adif.

At around 8:36 a.m., however, someone at the Adif center ordered a train owned by state operator Renfe to resume its trip, despite the red signal showing a stalled train further down the line. The Renfe train rolled 25 kilometers through an area where it could accelerate up to 200 kilometers per hour.

After about 15 minutes, it slammed into the idle train, which was owned by Iryo, a company controlled by Italy’s state-owned Ferrovie dello Stato.

“There was an order to restart the journey, there was time to correct that decision,” Puente said.

Antonio Hidalgo was on the Renfe train to Seville when it rammed into the other railcars. “I went flying down the hallway, and hit my eyebrow on the chair,” he said in an interview, pointing to a bandage above his eye covering 12 stitches. “Because my eyebrow was split open, I couldn’t see; I wiped away the blood and looked for my partner.”After derailing, the railcars tumbled down a steep embankment, scattering pieces of debris and metal under the midday sun.

Some of the carriages seemed to have been gutted from below, as if the train’s floor had been ripped off. Overhead, two helicopters whirred alongside eagles as they flew over an old train station nearby. Thermal blankets dotted the landscape.

Dozens of ambulances, cars and trucks whirred about. “It was Dantesque,” said Eva María Masías, the owner of a local cheese shop who got to the crash just before 10 a.m. to support the rescue efforts. “It’s a situation that you never imagine yourself facing.”When she arrived, emergency services were pulling passengers out of the trains. With her company’s trucks she brought water, blankets, chisels and compressors. Later, local residents helped drive survivors to a sports center in the nearby town of Urba.

“What struck me most was the look of utter bewilderment on people’s faces,” she said. “It wasn’t fear — it was a look that ... well, there are no words to describe it.”