"Motorbikes were his life. His room is filled with motorbikes," said Grigg.
He had loved motorbikes and quad bikes since he was 2 years old.
"He's been riding two-wheelers since he was 3 years old.
"It was a thing he loved to do."
Grigg said Saturday was like any other weekend with Brooklyn riding his bike round and round the back of the property.
"Everyone was keeping an eye on him.
"Unfortunately we have a stream running in the lower part of the property.
"On this occasion he was out of eyeshot and lost control and slid down the bank and landed in the stream.
"The bike had landed on top of him and he was fully pinned under, submerged in the water."
He gave CPR to his little boy straight away, trying desperately to get the water out of his lungs.
Volunteer firefighters and paramedics took over but could not save the youngster.
"They moved heaven and earth to do what they could but unfortunately it had been too long," said Grigg.
The family are now preparing to farewell the gorgeous, bike-crazy boy later this week.
"We just miss him so much," said Grigg.
"He was an awesome brother to his older sisters and he loved his mum and dad.
"We were looking forward to his life together.
"This is just a tragedy and something you never expect as a parent."
He said the family had been deeply moved by the show of community and church support since the accident.
"A lady who was cycling past when it happened, she came and dropped in a meal and flowers."
Friends from their Life North church congregation family were comforting them and neighbours were rallying at this difficult time.
Grigg praised the efforts of everyone who responded to the emergency.
He said the coroner was due to release a report into his son's drowning death and a funeral would take place on Friday.
