A 36-year-old man has been arrested on suspicion of the murder of nine-year-old Olivia Pratt-Korbel, Merseyside Police said.
Police said the murder suspect was also arrested over two attempted murders.
He is from the Huyton area of Liverpool and is in custody being questioned by detectives.
He was arrested after an operation involving armed officers in Merseyside on Thursday night.
Olivia Pratt-Korbel
Family Handout
The arrest came hours after Olivia's family appealed to people to “do the right thing” and help find out “who took our baby away from us”.
The schoolgirl died on Monday night after a man was chased into her home, in the Dovecot area of Liverpool, by a masked gunman, who killed Olivia and injured her mother Cheryl, 46.
In a statement released by Merseyside Police on Thursday, Olivia’s family said: “We as a family are heartbroken and have lost a huge part of our life.
“If anyone knows anything, now is the time to speak up. It is not about being a ‘snitch’ or a ‘grass’, it is about finding out who took our baby away from us.
“Please do the right thing.”
The family described Olivia, or Liv, as a “unique, chatty, nosey little girl who broke the mould when she was born”.
They said: “She loved life and all it had to offer.
Olivia died Monday night after a man was chased into her home by a masked gunman
Peter Byrne
“Liv loved dressing up and was very particular on how she was dressed, like any other little girl she loved doing her make-up and nails, she was nine going on 19.
“Liv was adored by everyone who knew her and would instantly make friends with anyone and everyone.
“She was often seen going up and down the street on her new bike she had just got for her birthday.
“Although her life was short, her personality certainly wasn’t and she lived it to the most she could, and would blow people away with her wit and kindness.”
Convicted burglar Joseph Nee, 35, from the Dovecot area of Liverpool, has been named as the intended target of the shooting.
As Olivia lay dying, he was picked up by friends in a black Audi Q3 and taken to hospital.
Police said the two people in the Audi had been traced and spoken to by officers.
Another man, who was with Nee at the time of the shooting on Kingsheath Avenue, had also been spoken to, the force said.
Nee has not been named by police but Mr Kameen said the 35-year-old man who was injured in the shooting remained in hospital and would be returned to prison following treatment after having his licence revoked.