The death of Joao Carvalho plays out to the back drop of an orchestra of screaming, excited fans, many of them children. Some leave their seats to run up to the wire mesh surround. Holding it with both hands they howl into The Octagon.

It will be 23 seconds before the sequence that leads to the death of Carvalho (28) finally ends with the referee indicating to Irish extreme fighter Charlie Ward that nine punches to the side of the head and face is enough.

The initial, far away view is of Ward and Carvalho wrestling upright against the far side of the ring. The two separate. Then, Ward cracks Carvalho with a right-handed punch to the side of the face. It is clean and hard, a “good” punch.

The Portuguese fighter staggers slowly backwards across the canvas to the near side of the ring, the two now exhausted and past that point where enduring courage and heart are no longer allies but common enemies.

Ward, responding to what hours of training in the gym tell him to do, follows across the ring. The Irish fighter swings with a left handed punch to Carvalho’s head but misses. He instinctively follows with a clean right to the side of the head, another “good” punch that knocks his opponent senseless.

Carvalho slumps down by the side of the ring. He is helpless and unable to defend himself. Ward senses his opportunity and falls on to him. He partially holds up the collapsed and dazed Carvalho with his heavily tattooed left arm, which fulfils two functions.

It presents a clean shot to the right side of Carvalho’s exposed head and face because he is held off the canvas. Ward also uses his opponent’s body as leverage to get power into his right handed punches, which rain down.

Seven of Ward’s nine punches to the right side of Carvalho’s head and face are long arcing blows, full punches. Carvalho does little to protect himself other than put his arm across his face. The referee stops the fight and the crowd explodes in delight.

Carvalho cannot get up but turns around onto all fours. He slumps to a sitting position and then sideways towards the canvas. His Saturday night in Dublin’s National Stadium ends in Beaumont hospital. He will be pronounced dead on Monday evening at 9.35pm.

In the debate of consenting adults making life choices, there is always a line to cross. It’s where disagreements in sport begin and in the anatomy of the death of Joao Carvalho the line is crossed because the sport allows it.

Ward cannot be blamed any more than the organisers, the promoters, the officials, Dublin City for permitting it to take place or the fans that pay to watch.

Many sports combine risk with aggression that puts health at risk. It happens in rugby and horse racing, in the TT Races at the Isle of Man and in boxing.

The decision of where to stop does not simply come down to what may or may not disturb some buttoned up sensibilities but, given the intentions of the fighters and how they go about achieving their aim, where it should stop is when it becomes obviously, dangerously violent.

In Hugh McIlvanney's 1980 account of the death of Welsh boxer Johnny Owen, he writes of the fighter's eloquence and self expression in the ring but outside of it an alien world where the chronically shy and inarticulate Owen sometimes didn't belong.

There is optimism and some truth to that and maybe also in the tragedy of Carvalho. But the end point of having few restrictions, the inevitable result of giving freedom of expression to warriors where extreme ferocity is permitted are weekends that by consent may end up in the city morgue.

The savagery of Carvalho’s beating and the glee of the young fans, unaware of what was unfolding but none the less aroused and stimulated by the extraordinary violence and perhaps now traumatised, will be seen in the broader sense as a calamitous and indefensible episode in Dublin.

There is no precedent in organised sport where punching a defenceless opponent nine times on the ground when he has collapsed but conscious is acceptable. It is crossing the line.

It exceeds boundaries because Ward was not only allowed to attack Carvalho but also because it was expected of him to do that. It is that aspect of the sport, one man struggling and helpless on the canvas and the other on top punching him again and again and again that makes it less a privilege of watching talented athletes and more an episode of cage pornography.

It brings people into a world that is more closely associated with assault and violence than any other sport including the regular whipping boy, professional boxing.

The athleticism and health of the fighters, their flexibility and stamina as exemplified by the face of MMA Conor McGregor, who was supporting Ward, doesn’t make it any less savage or safe. The money and notoriety of McGregor, the business that supports it or its popularity, especially among young people is no defence.

Perhaps that is the attraction, the lack of veneer. Real people. Real fighters. Real blood. Real hurt. The real McCoy of fighting. The children and teenagers in the National Stadium on Saturday saw their man Ward win. In time they will come to understand that what they witnessed was a legal killing.