The first attack was a large nail bomb hidden in a blue Austin car parked on South Carriage Drive in Hyde Park, along the route used by the Household Cavalry – Queen Elizabeth II's official bodyguard regiment – during the Changing of the Guard procession from their barracks in Knightsbridge to Buckingham Palace. Three soldiers of the Blues & Royals were killed instantly, and another died three days later from his injuries. The other soldiers in the procession were all badly wounded and shrapnel and nails sprayed into the crowd of tourists assembled to watch the parade, causing further injuries. Seven of the regiment's horses were also killed or had to be euthanised because of their injuries.