Traveling home on a high-speed train from Madrid to Seville in Spain, Fernando Seco was annoyed when congestion caused the train to stop about a half-hour after its 8 a.m. departure Wednesday. Not long after, it restarted, picked up speed and slammed into another train stopped on the tracks.

Mr. Seco, 62, and other panicked passengers climbed out of their carriage at the back of the train and into a field in central Spain. They saw the derailed carriages of the train they had barreled into in an embankment farther ahead. A rail beam, he said, had “pierced right through a carriage from bottom to top, like carving meat.”

He and others rushed to those carriages and found the dead and injured, those “trapped in a twisted tangle of metal and wreckage.”

The scene was eerily quiet because people were either dead or so hurt they couldn’t speak. He said survivors used parts of the destroyed train as makeshift stretchers to extract the injured from the wreckage. That’s when the screaming started. Doctors among the passengers treated people in what became a field hospital among almond groves.

At least 68 people died in the crash. More than 50 others were injured, some critically.

Spain is living through a recurring nightmare. For the second time in less than a year, a high-speed crash between the same two train operators on the same busy line from Madrid to Seville threw the country into official days of mourning, shook its confidence in the security of it once-vaunted rail system and undercut its international image as a modernizing tourist mecca helping to thrust Europe forward.