MADRID — An armed group attacked the North Korean Embassy in Madrid last month and then fled. Neighbors reported hearing a woman’s screams, but the embassy did not want to discuss the events with the Spanish police.

On Tuesday, the story got even stranger.

A Mexican man who lives in the United States led the raid, and later offered material stolen from the embassy to the F.B.I., a Spanish judge investigating the case said.

In a summary of his investigation, José de la Mata, a judge of Spain’s national court, identified the leader of the gang as Adrian Hong Chang, who he said had escaped, through Portugal, to the United States. An American citizen, identified as Sam Ruy, was also involved in the Feb. 22 assault, he said.

The judge later issued international arrest warrants for both suspects, according to an official from the court.