The victim was shot in the chest at close range, while sat in a car in a parking area behind Flint Close, Luton, just after 11pm on Friday, November 8, 2019.
Three young men on push bikes and wearing masks were involved in the shooting.
They arrived at the scene, opened up the passenger door of a parked silver Vauxhall Corsa and opened fire.
Youths spotted deliberately damaging fencing along the Luton to Dunstable busway
Picture shows aftermath of field fire in Sundon Park Road in Luton
Luton's Wigmore Park needs your vote in contest to find the nation's top green spaces
Avoid Sundon Park Road in Luton as firefighters tackle field blaze
Luton commuters: Only travel if absolutely necessary this weekend
The victim, a man in his 20s, was left with serious injuries after being wounded in the chest.
Detective Inspector Philip Moss, from the Beds, Cambs and Herts major crime unit, said: “This cowardly and reckless attack represents violence of the absolute highest degree.
“The unsuspecting victim was shot at close range before the three attackers left the scene on their bikes.
"This simply cannot be tolerated. Someone will know who is responsible for this.
“I would ask them to think about how they would feel if any of these three people went on to commit similar acts of violence against someone they know, knowing that the information they hold now could have prevented that from happening.
“Our investigation has achieved a great deal, including taking a firearm off the streets, but we now need those with any information to come forward, so we can do our job and bring these clearly violent offenders to justice.
“You don’t have to talk to us – you can give any information or names anonymously via Crimestoppers.”
Anyone with any information about the shooting should contact police through the Bedfordshire Police website or by calling 101, quoting Operation Maldon.
Alternatively, contact Crimestoppers anonymously by calling 0800 555 111 or visiting https://crimestoppers-uk.org.