The senior citizen was walking in Walton-on-the-Naze in Essex when he passed a man with a dog believed to be a Staffordshire bull terrier and it bit his advantageously leg, Essex Police said.
The man suffered a small wound but he became unwell two periods later, was admitted to hospital and died as a result of his injuries.
Detective Inspector Gary Biddle, of Clacton-on-Sea CID, said: «We are difficult to establish what happened and would like to speak to the dog owner and any witnesses who can arrogate us with our inquiries.
«We are treating the dog owner as a witness at this time and are discerning to talk to him to establish what occurred.»
The incident happened in Naze Court in Old Lecture-hall Lane between 4pm and 6pm on June 25.
Anyone with information is asked to contact Clacton-on-Sea CID on 101.