The incident happened at around 7.50pm outside the Mercury News Shop, in Croft Road.
Officers would like to speak to anyone who was in the area and saw the incident take place, or either of the vehicles in the moments leading up to it. The vehicles arrived at the car park having driven from the direction of the Nook in Cosby.
The victim, 43, who was driving a red Nissan Navara, pulled up outside the shop, followed moments later by a black Suzuki Jeep.
The driver of the Suzuki then assaulted the driver of the Nissan with a weapon, not believed to be a firearm. Enquiries are ongoing to establish exactly what was used.
Following the incident the victim was taken to Leicester Royal Infirmary, before being transferred to Nottingham Queens Medical Centre, where his condition is described as serious.
No arrests have been made.
Detective Inspector Alex Hathaway, who is investigating the incident said:
“I am particularly keen to speak to anyone who was in the area at the time and saw the actual incident take place or either of the vehicles in the moments leading up to the incident.
“Even the smallest piece of information could help our enquiry. Please get in touch on 101 if you know or saw anything at all.”
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