A teenager was injured during a second shooting in a day in Walton.
Emergency services were called around 2.45pm on Friday to reports that a man had been shot in the leg outside a property on Church Road West.
The offenders are believed to have left the scene in a blue Volkswagen Golf car.
A 19-year-old has been taken to hospital for treatment to a single injury to his leg consistent with a firearms discharge.
His condition is described as stable and his injury is not thought to be life-threatening.
At this early stage of the investigation, the full circumstances and motive of the incident are unknown but it is believed to have been a targeted attack.
Officers and Crime Scene Investigators are in attendance at the scene and extensive enquiries are being carried out to establish the full circumstances of what happened and locate the offenders. CCTV from the area will be sought.
A cordon has been established to allow for forensic examination of the scene and house to house enquiries are being carried out.
High visibility patrols have been stepped up in the area to provide reassurance to the community.
Superintendent Mark Wiggins said: “The investigation into this incident is in its very early stages and we are keeping an open mind as to why this has happened.
“Criminals who choose to settle their disputes with a weapon do not care about the fear they bring to communities in Merseyside.
“We need the public to help us make the streets safer by telling us what they know about these criminals.
“I promise we will take robust action and put these people before the courts and in prison.
“If you know something, please pick up the phone and let us know.
“If anyone witnessed the incident or saw anything suspicious that could help us investigate it then please contact our gun crime hotline on 0800 230 0600 or leave information anonymously with Crimestoppers on 0800 555 111.”
Earlier on Friday, a man was arrested after shots were fired outside Walton prison.