Detectives are appealing for information follow an incident in Mill Hall par park, Rayleigh, on Wednesday October 14.
A man in his 50s was returning to his van when he saw two men attempting to take the tools stored inside.
The men attempted to make off in a Silver Vauxhall Astra, but in the process hit the man and then drove off in another car, a Blue Volkswaen Estate, which was parked nearby.
He was taken to hospital with a back injury.
The first man is described as being of a large build, tall and in his 40s. The second man was described as in his late ten to early 20s.
If anyone saw the car or what happened, have CCTV of the area or dash cam footage please call 101 quoting crime reference 42/167277/20.
You can also report anything online at www.essex.police.uk