The 56-year-old was found within the grounds after a member of the public raised the alarm at 8pm.
Police went to the scene, located him and he was rushed to hospital with serious head injuries.
He died this afternoon.
A post mortem examination will take place in due course to establish the exact cause of death.
Police Scotland said: "Enquiries are continuing to establish the exact circumstances surrounding this incident and Detective Inspector Mark Bell from the Major Investigation Team (West) is appealing to anyone with information to contact Police Scotland on 101. Alternatively CRIMESTOPPERS can be contacted on 0800 555 111, where anonymity can be maintained."
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