A man who tried to ram his car into the Dutch royal family, killing six onlookers at a parade, died in hospital yesterday as details emerged of how he lost his job and was about to lose his home.

The killer driver, who has not been officially identified, died in hospital in the early hours from severe head trauma as relatives of the six victims that he mowed down tried to come to terms with their loss.

The tragedy, labelled "an act of despair" by newspapers, also prompted questions about royal security and whether there would have to be a rethink about staging the annual Queen's Day procession.

Newspapers, displaying gruesome photographs of twisted limbs and bodies sent flying at a royal parade on Thursday in the central city of Apeldoorn, said the man had recently lost his security guard job.

"Recently, he informed me that he had been dismissed and could no longer pay the rent," landlord Sem Bosman told the mass market De Telegraaf newspaper.

"He was due to have come today to transfer the keys to a new tenant."

The 38-year-old was described by his former landlord and neighbours as quiet, solitary, friendly, soft-spoken and a "dark horse".

The tragedy happened when the driver of a black Suzuki passenger car deliberately slammed his vehicle into Queen's Day party goers in full view of Queen Beatrix, Crown Prince Willem Alexander and his wife Maxima among other members of the royal family in an open top bus, which had been the target.

The car missed the bus and rammed into the foot of a monument, leaving injured people and battered bicycles in its wake.

Two men and two women died shortly after impact. A third man died in hospital later Thursday, followed overnight by the driver himself.