Yusuf Sonko was shot in Liverpool in June 2017. He was 18 years old.
In the past 18 months there have been five fatal shootings in Merseyside, but no one has been charged for the killings.
Merseyside Police say a lack of resources has made tackling gun crime harder, but the Home Office says it is working with police to find a solution, and lays the blame for the rise in gun crime on gang leaders.
You can watch the full programme; Panorama: Police Under Pressure at 21:00 on 16 May on BBC One, or on iPlayer.