Casey Breese was enjoying a game of footie with his friends when it is thought he caught his foot in the net, bringing the framework of the goal crashing down on his neck.
Paramedics treated the youngster at the scene and he was taken to hospital by air ambulance, but pronounced dead shortly after arrival.
His devastated granddad Selwyn told reporters the family are in 'shock and disbelief', adding: 'We demand to know how something like this happened to our wonderful boy. I want answers as soon as possible about who's to blame for this tragedy.
'He was a great lad who lived for football. His mum Shan and dad Nick are in bits. His three older sisters adored him and I don't know how they'll ever get over this. Our family is devastated.'
After the incident the goals - which were not full size - were taken away for examination as a police and health and safety executive investigation got under way.
Friends and family left tributes to Casey at the scene, including flowers and a red football shirt with 'Casey 1' written on it. Flowers left by one of his three older sisters, Kelly, read: 'Hope you're having fun up there and not getting in too much trouble.'