Something doesn't make sense to me: Guy became a felon in 2004, but is involved in a shooting in 2006, and now the feds suspect he might have illegal access to

Something doesn't make sense to me: Guy became a felon in 2004, but is involved in a shooting in 2006, and now the feds suspect he might have illegal access to firearms (because felons aren't allowed guns) - how did he not get popped for that after the shooting in 2006?