AMSTERDAM — The man who drove his car into a crowd of parade spectators and killed five people died of his injuries today, leaving unresolved the mystery of why he tried to attack the Dutch royal family.

The 38-year-old suspect, identified by Dutch media as Karst Tates, had been in critical condition since the attack Thursday on Queen's Day, the Dutch national holiday.

Eleven other people were hurt when he rammed his car through police barricades toward an open-topped bus carrying Queen Beatrix and several other members of the royal family.

He told one of the first police officers to rush to his car the attack was aimed at the royal family, prosecutor Ludo Goossens said Thursday. But the motive was unclear.

"It is very difficult now that we no longer have the suspect to reconstruct what was behind this," said Fred de Graaf, the mayor of Apeldoorn where the incident occurred.

"An element of uncertainty will remain because you can no longer question the suspect. So the last piece of the puzzle will remain in question," he said.

Dutch media, citing neighbors, said Tates recently was fired from his job as a security guard and was to be evicted from his home in the small eastern town of Huissen because he could no longer afford the rent. Police said he had no history of mental illness or police record.

The neighbors described him as friendly, but a man who kept to himself, the NRC Handelsblad newspaper reported on its Web site.

Prosecutors said the suspect's death ended the criminal investigation against him.