British police arrested four people in connection with the killing of an 11-year-old boy in Liverpool.
Police also urged a witness who had called a police "hot line" a week ago with information about the shooting to identify himself and come forward to be interviewed by authorities.
Rhys Jones, 11, was shot in the neck Aug. 22 as he returned home from playing soccer in Liverpool, northwest England, and police believe he may have been the unintended victim of gang warfare.
The case also started a debate in Britain about the effectiveness of the country's strict gun-control laws.
Two men, aged 20 and 24, and two boys, aged 17 and 16, all from the Liverpool area, were detained by police on Friday for questioning.
The arrests raised to 15 the number of people who have been taken into custody in the case. The other 11, most of them teens, have been questioned and released on bail or freed without charge, police said.