A 15-year-old boy has been arrested on suspicion of murdering Rhys Jones, Merseyside police have said.
Rhys was shot as he walked home after football practice
Rhys, 11, was shot by a teenager on a BMX bike near the Fir Tree pub in Croxteth, Liverpool, as he walked home from playing football last Wednesday.
Det Chf Insp Dave Kelly, leading the investigation, has also appealed to one man who has already called police to contact them again.
The latest arrest brings to 11, the number of people quizzed by police.
Det Chf Insp Kelly said there were still people "who have not yet come forward".
"I know there are still people out there that will provide key information that will bring this killer to justice," he said at a press conference on Wednesday," he said.
"We need to trace everybody who was in this area. You may hold vital information."
"There is one man who has rung in and provided key information and I thank him for making that call. He is very brave.
"I will personally speak to you and I will look after you by whatever methods we have available to us.
"I would like to say this to the killer. What you have done is wrong, we need to deal with you.
"It is only a matter of time before we get you. Please come forward for the family's sake."
Officers searched nearby Dam Wood on Tuesday after a tip-off from a member of the public.
A total of 46 officers, supported by police sniffer dogs and specialist equipment, combed the wood between Croxteth and the Croxteth Park Estate.
Divers joined the search of the woodland which contains three large ponds.
Detectives had previously arrested and released 10 teenage suspects, four without charge and six on police bail.
They have also pledged that anonymity will be given to witnesses.
Special measures have been agreed with the Crown Prosecution Service to ensure those who give evidence in court will be allowed to use video links or sit behind a screen.
Liverpool fans put aside football differences on Tuesday night
Some potential witnesses have been reluctant to reveal their identities or give signed statements.
Assistant Chief Constable Patricia Gallan, of Merseyside Police, described call to the Crimestoppers number as "fantastic" and pledged that all information would "be acted upon".
But she added: "We now need to make that information into witness statements. I know that can be a big step for people who are concerned for their identity.
"But special measures can be taken to protect them in the courts.
"We can protect them and we will help them bring Rhys's killer to justice."
Police will later mark a week since the murder by stopping motorists and members of the public outside the Fir Tree pub, in an appeal for further information.
'Z-cars' theme tune
Leaflets have been supplied by Tesco, where Rhys's parents are employed.
On Tuesday night Rhys's family was given a standing ovation by thousands of football fans at Anfield, the home of Liverpool FC.
Liverpool manager Rafael Benitez walked along the touchline to hug Rhys's mother Melanie, 41, and shake hands with his father Stephen, 41, and brother Owen, 17.
The family were wearing the blue colours of local rivals Everton FC in a sea of red but football loyalties were set aside.
The Everton theme tune to the Z-Cars TV series was played as the players arrived on the pitch for the game against Toulouse.
Messages were also broadcast over the public address system ahead of the match appealing for witnesses to the shooting to come forward.
Footballer Steven Gerrard has also spoken out in support of the police investigation.
"The reception that Rhys's family got at Anfield last night was fantastic and showed that everyone in the city has been affected by this tragic event," he said.
"I would appeal to anyone, who has any information at all, to please contact the police and help find those who were responsible for this terrible crime."