A man reportedly "charged" at an 11-year-old boy with a brick and then stole the youngster's bike at a Fishponds play park in broad daylight.
The victim's dad Jon, who didn't want to reveal his surname, said his son was 'physically shaking' and in shock when he rushed to Vassals Park to pick him up.
"You try and look after your kids and give them a sense the world is a fair place and if they do the right thing they will be alright but this has shaken his perception now," said Jon.
"He was in complete shock, he had been threatened by an adult who was being completely unreasonable."
Jon says the drama unfolded at around 4:25pm on Saturday (January 25) after his son approached a child who was upset because someone had stolen his back tyre off his bike. They reportedly chatted briefly before the child ran off to find his parents.
According to Jon's son, moments later, the child's dad charged at the victim and his friends with a brick.
The 11-year-old ran away, leaving his bike behind.
He says he then saw the man, who is described as being in his mid-30s, medium build, with a beard, take his £400 BMX into a white van and drive off.
Avon and Somerset Police has now launched an investigation into the theft.
A force spokesman said: "We were called at 4.25pm to reports of a bike theft at Snuff Mills car park on Saturday.
"A man carrying a brick is said to have taken a bike belonging to an 11-year-old boy. There are no reports of any injuries.
"The man is described as being about 30 years old, white, having a brown/ginger beard and wearing shorts. He is said to have loaded the BMX bike into a white van.
"Enquiries are ongoing.
"Anyone with information about what happened can call 101 and quote log number 0771 for Saturday 25 January."
