Soldato
So if the USA/UK with the most capable intelligence services in the world still haven't found Jihadi John, how exactly is Egypt going find whoever committed this atrocity? I fear you're underestimating how difficult it is for security services to operate in areas controlled by Islamic State, which is why of course, their strategy is based on occupying land.
Who is to say we haven't found JJ already? you're right that it's very difficult though.