Ángeles Pedraza, the president of AVT, one of the largest victims associations, said she did not believe that the terrorists involved in the meetings were sincere. “How strange that in 50 years no one ever phoned the victims to ask for forgiveness,” she said. “This is only happening now.”

Image Hundreds were killed in a bid for Basque independence. Credit... The New York Times

For Mr. García, who teaches marketing at Deusto University here, the decision to talk to the former terrorist was difficult. He told no one in his family. And he first made sure that the prisoner would not benefit in any way from sitting down with him. Still, on his way to the meeting, his car got a flat tire and he wondered whether it was a sign that he should turn back.

The two men spoke for more than two and a half hours, each telling his life story. Mr. García found out that, in fact, it was hard to look someone in the eyes and shoot him. In one case, the terrorist said, it was that look that had saved someone’s life. But Mr. García also found out that ETA assassins usually knew nothing about their targets. They were simply given photographs and told to kill at a certain hour. At first the job was taxing. But then killing became routine, the terrorist told him. For Mr. García, the most emotional moment was when the terrorist, now in a work-release program, said he was sorry. Mr. García said he saw that the man was profoundly ashamed for what he had done.

“That was tremendous for me,” Mr. García said. “I said I accepted his apology. But I said he needed to talk to the families he had hurt, and I told him he was, well, brave.”

The two men have met several times since for lunch and keep in touch by e-mail.

Another convict, Iñaki Rekarte, 42, who has spent nearly half his life in prison, sentenced to 203 years for acts of terrorism that included a car-bomb explosion that killed three bystanders, said he was in a total panic as the hour for his meeting with an elderly victim approached. “I was stuck on the basics,” he said. “How do I greet her?” The Spanish kiss on first greetings. But would that offend under the circumstances?

He said he was not expecting forgiveness; that seemed an almost frivolous idea. “It’s not like you had a fight with your neighbor and you say, ‘Oh, sorry.’ ” he said. Mr. Rekarte has served more than 18 years behind bars, but is now free to leave the prison during the day. He has married and has a child of his own. He said he wanted to try, at least, “to do something good” for the relatives.

The Basque Department of Victims reached out to the father of one of his victims, offering a meeting. But the father, now 80 years old, refused. Instead, Mr. Rekarte sat down with an elderly woman whose husband, a small-town politician, had been assassinated.