Profile Emerges of Suspect in Attack on Train to Paris

LONDON — The young man who emerged from a Thalys train bathroom on Friday with a Kalashnikov assault rifle, pistol and box cutter is believed to be Ayoub El Kahzani, 26, of Moroccan origin, who was known to the Spanish and French security services and is reported to have traveled to Syria last year.

With the man under interrogation by French antiterrorism authorities, who can hold him without charge for up to 96 hours, French officials cautioned that many details of his life, and even his identity, had yet to be confirmed.

But if the outlines of his profile prove correct, in particular that he had already been identified by officials as a potential threat, the case may once again underscore the challenges European authorities face as they try to keep track of several thousand people in Europe who have circulated to and from Iraq and Syria to join jihadist groups.