Paramedics performed emergency surgery on a 66-year-old man at the scene, but he suffered a cardiac arrest and was pronounced dead.
His brother, who is in his 70s, also suffered chest injuries.
He was airlifted to Frenchay Hospital near Bristol, where he remains (Tuesday).
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Bristol Mayor George Ferguson has been accused of a "nasty personal attack" in a row over how the city's Green Capital cash was spent.
Bristol Mayor George Ferguson says there will be "further breakdown" of how the city's Green Capital cash was spent.