The family of a man found murdered in Swanbourne last week says not knowing what happened is tearing them apart.

Major Crime Squad detectives are appealing for public help as they investigate the death of 32-year-old David Liam Johnson.

His body was discovered with a gunshot wound to the head in a park just after 11 pm on Friday at Lime Kiln Field.

Mr Johnson's aunt, Jennifer, has publicly pleaded for anyone with information on the murder to come forward and ease the family's grief.

"I think that's always the part that tears people apart, tears families apart, tears individuals apart, that element of not knowing," she said.

Detectives are calling for anyone with any information about the incident to call the relevant authorities.

They say they believe someone in the community knows who is responsible for the murder.

Police have yet to determine a motive for the shooting.