Detectives in Liverpool have released on bail a 15-year-old boy they were questioning in connection with the murder of 11-year-old Rhys Jones.
Rhys was shot as he walked home after football practice
The boy was the eleventh teenager to be questioned by officers over Rhys' shooting on 22 August.
On Wednesday evening, Merseyside Police stopped people near the scene of the killing in Croxteth, in the hope of finding fresh witnesses.
They have also appealed for a man who had "key information" to call them.
Det Supt Dave Kelly, from Merseyside Police, said the man had called them on Saturday at about 2320 BST.
He said police promised to look after him if he called back.
Rhys, 11, was shot by a teenager on a BMX bike near the Fir Tree pub in Croxteth as he walked home from playing football.
Det Supt Kelly, leading the investigation, 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.
"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 searching nearby Dam Wood near the Croxteth Park estate have discovered two guns but said they were not connected to the fatal shooting of Rhys Jones.
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.
Rhys's parents have urged their son's killer to surrender to police
Some potential witnesses have been reluctant to reveal their identities or give signed statements.
Assistant Chief Constable Patricia Gallan, of Merseyside Police, described calls 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."
Mr and Mrs Jones have urged their son's killer to surrender to police.