The only source I've seen is the Daily Mail, so for all I know this is totally fake. That said, I suspect no prison can mean 1 of two things: house arrest or put into a "camp" for wayward "teens" that's not a prison, but you can't leave. Or it could be probation. For all I know they were allowed to plea to not-murder. Prosecutors have an enormous amount of discretion. Most times and places they are out to get the maximum possible sentence for stealing a stick of chewing gum. Obviously here, something happened.