It happened on the B3081 near Verwood - he had to be cut free by firefighters.
Boy Dies From Head Injury In Southampton
Police were called to a house in Shirley, where they found a 7-year-old with a serious head injury - he later died in hospital.
Two men have been arrested after a seven-year-old boy died after suffering a serious head injury, police said today.
Police were alerted just after 7pm on Saturday evening after the boy was taken to hospital from an address in Cromarty Road, Shirley, Southampton, Hampshire.
He died the following day from his injury.
A Hampshire police spokeswoman said: "Police officers in Southampton are investigating the circumstances in which a seven-year-old boy from the city received a life threatening head injury from which he eventually died.
"Officers are continuing to investigate how the boy came to receive the injury, and as part of that investigation a 23-year-old man and a 21-year-old man, both from Shirley, were arrested on suspicion of causing grievous bodily harm.
"They have since been released on bail until March 6 while investigations continue.''
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