An 83-year-old man was stabbed to death while he was walking his two dogs, Norfolk Police said.
The pensioner, who is described as a family man from Norfolk's East Harling area, was repeatedly stabbed in the neck and head.
A member of the public found his body in woodland near the Fiveways Junction on Saturday and called police at 10.45am.
A murder investigation has been launched.
A post mortem found he had died from multiple stab wounds to the neck and head.
Norfolk's County Police Commander Chief Superintendent Mike Fawcett sought to reassure residents.
Mr Fawcett, who said "the motive remains unclear", added: "I fully understand that residents will be shocked and concerned that a murder with this level of brutality can happen to an elderly man going about his daily business in our county."
He urged anyone who has noticed any unusual activity in the area recently to come forward.
He said: "Those who use the woodlands and footpath regularly, especially whose who were there between 9am and 11am on Saturday 5 August, are urged to contact us."
Uniformed officers and a mobile police station have been set up at the scene.
Local police patrols have also been increased.