The victim, who had been seated in the front passenger seat, was taken to hospital with a leg injury.
Merseyside Police said police were called to the scene at Mcdonald’s in Welton Route, Bromborough, at 5.30 pm, according to reports of the shooting.
The force has since launched a manhunt for the suspect, described as an Asian male, around 5’8 “tall, medium build, with a beard and wearing a black hooded jacket.
He is said to have left the scene in the direction of an Asda supermarket.
A cordon is also in place while a VIDEO SURVEILLANCE system is reviewed, with witnesses and judicial investigations underway.
Speaking for the Liverpool Echo, a witness said she heard “three or four shots” and at first thought it was “a joke”.
She said: ” [The gunman] ran on the New Chester Road and straight to the car window. I think it was like three or four shots and then the car accelerated out of the parking lot and the boy fled.
“The staff came to tell us they were closed, but we had to wait for the police. I can’t believe it – there are loads of people in the queue, everyone seen from him. ”
Detective Inspector Paul Parry said the investigation was still in its infancy and urged everyone who was in the area to get in touch.
He added: “I understand the alarm this incident caused, as it happened in broad daylight in a busy area with a number of people around, but rest assured that we are doing our best to find the person responsible and the patrols will remain in the domain of reassuring and gathering information.
“If you witnessed the incident, or in the event of a CCTV, footage or information dashcam, please let us know, as it could prove to be vital to the investigation.
“The murder weapon will not be tolerated on the streets of Merseyside and we will continue to be always on the lookout for those involved in serious and organized crime. ”
You can contact the force directly via @MerPolCC, by calling 101 citing ref. 20000355196 or the independent Crimestoppers anonymously on 0800 555 111