Lee Irving, who had learning difficulties and was described as "vulnerable", was discovered on a grassed area in Newcastle on Saturday.
Four men and one woman have been arrested on suspicion of murder.
Northumbria Police said they are investigating whether Irving's learning difficulties were a factor in his death.
Superintendent Bruce Storey said: "It's thought those involved in this incident know each other.
"Lee had learning difficulties and was vulnerable. One of our key lines of inquiry was to establish whether this is a factor in his death and a motivation in this crime."
Emergency services were called to an area near a pathway between Dorrington Road and Hazeldene Avenue in Fawdon at around 8.34am. The area is a popular route for dog walkers and cyclists.
Irving, from Camperdown, East Denton, was declared dead at the scene and a post-mortem examination has been completed.
Police said the local community are "shocked and appalled" by Irving's death and extra officers are carrying out patrols in the area to offer reassurance.
Officers are appealing for witnesses and want to speak to anyone who was in Fawdon between 7am and 9am on Saturday morning.
Mr Storey added: "It's important those suspected of being responsible face the consequences of their actions and I would urge anyone who was in Fawdon on Saturday morning, between 7am and 9am, to come forward and speak to us. If they saw anything at all that seemed out of the ordinary, no matter how insignificant they think it is we would ask them to get in contact."