The suspect was known to the woman whose body was found with a gunshot wound, police say.
A 79-year-old man has been arrested over the fatal shooting of a woman, say police.
The body of the woman, believed to be in her 50s, was found by officers in a house on Meadowbrook Road, Moreton, at about 01:45 BST, Merseyside Police said.
They said she had “an injury to her chest consistent with a gunshot wound”.
The arrested man, who was known to the woman, was detained on suspicion of murder. He remains in custody.
Police are appealing for anyone with information to contact them.
Ch Insp Derek Riley said: “Although a man has been arrested following the tragic death of this woman in Moreton, we are still in the very early stages of our investigation and inquiries into the incident are still ongoing in the area.
“I would ask anyone who was in the area of Meadowbrook Road in the very early hours of [Sunday] morning who saw or heard anything, or thinks they have captured anything significant on their doorbell camera or dashcam, to contact us as a matter of urgency.”