The target was a pop concert, the audience was a mixture of teenagers, many of them young girls, all out for a fun and innocent evening. Some were young enough to need chaperoning by parents or grandparents.
If this does turn out to be an Islamist-inspired attack, the attacker has deliberately targeted everything his warped beliefs hate in a Western society.
He has also demonstrated a deadly competence - he blew himself up as the high-spirited crowd streamed out of the arena after the concert. The timing, and location of the explosion - just outside the main arena itself - suggests planning and shows he probably carried out a recce.
The singer Ariana Grande is world-famous. She has more than 45 million followers on Twitter. Another basic but twisted way of guaranteeing this attack will resonate far.
The morning after the attack, a number of things will be happening simultaneously and with urgency.
In Manchester, counterterrorism police from North West Command will be carrying out forensic work at the scene of the explosion.
They will try and find bomb-making signatures that might give a clue as to who was behind this attack.
They will look for certain chemicals, such as triacetone triperoxide (TATP).
TATP has been used by terrorists around the world, it is a favoured compound of Islamic State and it is relatively straightforward to make, but it is extremely unstable and lethal.
It has been confirmed that the attacker died on the scene - this tells us that something is left of his body.
That will be important in identifying him, either facially, through fingerprints, dental records or DNA. Once they know who he is, databases will be scoured. Was he known to the security services? Does he have known associates?
His home will be searched. So too the homes of any close relatives or friends.
People might be detained, questioned and then released. Computers will be taken away and their contents and internet history studied.