Sean Mercer, 18, has been found guilty of murdering Rhys Jones in Liverpool on 22 August 2007.
So what exactly happened in Croxteth that evening?
Rhys Jones, an 11-year-old Everton fan, was walking back from football practice - when he accidentally wandered into the path of a gang member - Sean Mercer.
The police say that Mercer had received a call telling him that members of a gang that he hated were hanging round a pub that he went to, on his 'territory'.
Mercer cycled to the pub and fired three shots across the car park, towards the rival gang members who were there. The second of the shots hit Rhys in the neck and killed him. Rhys happened to be in the car park at the time and knew nothing about the rival gangs.
Sean Mercer was caught on camera
After the shooting, a CCTV camera captured Sean Mercer cycling away.
He dumped his bike and his gun and burnt all his clothes. He thought he had destroyed all the evidence which linked him to the crime. Mercer was helped by other members of his gang, who hid evidence for him and helped him lie to the police.
Five members of his gang were also found guilty in court of helping an offender.
People across the country were shocked by the killing and there was a massive search for information.
The police sent out text messages asking anyone living in the area if they'd seen anything.
Police at the scene of the shooting
But they were soon onto Rhys' killer - tracking his mobile phone signal and filming what he was up to.
They spent months gathering information about what happened. It took so long because they wanted to make sure they had lots of evidence when they went to court.
But what about life in Croxteth - a year on?
Rhys would have been 12 in September
The trial heard how there are two rival gangs in this area. One is called the Strand Gang, the other is named the Croxteth Crew.
They've been fighting each other for years. They aren't just groups of people hanging out together. Members of the gangs were involved in breaking the law.
Even before Rhys' killing the police had set up a special team to crack down on dangerous gangs, called Operation Matrix.
Croxteth's schools have their own police officer who can keep an eye out for trouble and listen to people's problems.
Rhys's family reckon they can make a difference by building a community centre in his memory.
Rhys's mum and dad
They've been raising money along with friends from his old football team.
And people across Liverpool are working hard to make sure that there aren't any more innocent victims like Rhys Jones.