Synchronised, winner of the Cheltenham Gold Cup just a few weeks ago, and According To Pete both had to be put down after falls during the legendary race at Aintree.
The deaths marred what was otherwise a spectacular renewal which saw 33-1 shot Neptune Collonges beat Sunnyhillboy by the closest winning margin ever seen in the iconic race.
The two deaths are anything but isolated incidents: earlier in the week at Aintree, Gottany O's had to be put down after stumbling and breaking a leg while leading a race.
In March five horses were killed during the four-day Cheltenham Festival meeting, while the Dubai World Cup was also marred by three deaths in a supporting race at Meydan racecourse in the United Arab Emirates.
Racing regulators are again investigating the tough jumps at the Grand National track - and in particular the infamous Becher's Brook, with its 6'9" drop on the landing side. The jump, described by jockeys as "like jumping off the edge of the world", is where Synchronised unseated his champion jockey Tony McCoy, though the horse continued to run without its rider and sustained its fatal injury at a later fence.
Professor Tim Morris, Director of Equine Science and Welfare for the British Horseracing Association, insists that the organisation take the responsibility of looking after the welfare of horse and rider "very seriously".
But the RSPCA's equine advisor David Muir is unequivocal: "The death of a horse is the unacceptable face of horse racing," he said. "I am not happy with the drop fences and Becher's is a drop fence."
Changes to the fences at Aintree are expected, though there had already been modifications in the course after last year's race - an event which also claimed the life of two horses.