Police are seeking a female dog walker after a rider died following a fall while hacking in Gloucestershire last week (4 March).
Two riders fell in the incident, which happened in Bisley Camp, Stroud, at around midday.
A 52-year-old man was taken to Southmead Hospital, Bristol with serious injuries and died earlier this week (Monday, 9 March)
A female rider broke her collarbone in the fall.
Police are now urging a walker, whose dog was “involved” in the incident, to come forward as they believe she has “crucial information about what caused the riders to fall”.
“She is described as white, in her 50s, 5ft 6ins tall, of average build, with blonde/grey hair which was chin length and appeared naturally curly,” a police spokesman said.
“Her dog was a black and white border collie that was noticeably ‘roughed or fluffed up’, giving the impression it was a home dog, not a working dog.”
It is thought the woman might have been wearing blue and white clothing. It is not clear if she was local or visiting the area.
A police spokesman added that although the dog was “involved” in the accident, it was not necessarily “responsible for the incident” as full details are still to be investigated.
The dog walker or anyone with further information is urged to call 101 or 01452 726920, quoting incident 179.
After changes to the law, which came into place last May, dog owners can now be prosecuted if their dog causes injury to a rider on public and private land.
It was already an offence under the Dangerous Dogs Act for any dog to be dangerously out of control in a public place.
There is concern from within the equestrian industry about the growing number of dog attacks on horses.
In 2013 H&H reported that the number of dog attacks on horses had almost doubled in the past year, according to the British Horse Society.
The organisation urges all horse owners who have suffered an attack to report it at: www.horseaccidents.org.uk