Why is murder so entertaining? If a man walks into a cinema and guns down a slew of people, as American student James Holmes did last summer, the world reels with horror.
Yet many of us have no problem watching similar scenes of murderous violence on the big screen – and even enjoying it.
There can be something almost narcotic about it, as in Quentin Tarantino's brilliantly brutal new film, Django Unchained. It's shocking, transgressive and weirdly exhilarating.
Sick? Maybe. But as long as it's the good guy pulling the trigger, you relish every shot.
The reality, of course, is very different. Here in Northern Ireland, it's not surprising that we have a particularly uncomfortable relationship with violence.
Because of the close proximity of the past and the terrible toll inflicted on victims, we know – from hard, bitter experience – that murder is no comic-book fantasy, still less a one-off event. The fear, pain and loss go on resonating down the generations, replicating the evil.
It often finds expression in alcoholism, mental illness and suicide, which carries the trauma on into the next generation and so on.
There is no honour, no glory, no gain, just the inexorable trajectory of a single vicious act of unspeakable cruelty. This is one bullet that may never stop.
And yet, in spite of the horror, a secret fascination with our awful past still lives on in many of us. We are repulsed yet intrigued; disgusted yet curious. Now a new Troubles tour of Belfast aims to satisfy that curiosity. A History of Terror explores 12 sites around the city centre where people lost their lives, through shootings, bombings and beatings.
Although it is intended as a tourism venture, the organisers say that many local people, including PSNI officers, have been booking places on the tour.
DC Tours (DC stands for Dead Centre, which seems a little insensitive, to say the least) insists that there is nothing sensationalist, or macabre, about it.
According to them, it's non-political, objective and factual. Apparently, the tour has also been vetted by Belfast City Council to ensure appropriate accuracy and absence of bias.
Very plausible, but I'm afraid I don't buy the idea. For instance, putting a picture of a masked paramilitary brandishing an AK-47 on your website, as DC Tours do, along with the caption 'Experience the Terror' is salacious, tasteless and gratuitously offensive. Really? Experience the terror? This is not an action film, or a computer game. This is real life, real death, on the streets of our city. Don't reduce it to a glib soundbite and a cheap thrill.
And while the organisers have been careful not to include more recent murders in their tour, that does not absolve them of responsibility.
The closest incident to the present that they cover is the killing of RUC officer James Douglas, who was shot dead on October 10 1992 in the Monico Bar in Lombard Street. But 20 years is nothing to a grieving family. I wonder how they feel, knowing that the site of their loved-one's murder is now part of a Troubles tour.
For all the language of equality and respect, for all the official imprimatur of the Belfast Welcome Centre (that's where you can buy tickets at a tenner a pop), this tour is essentially a commercial enterprise.
It's not a charity, so presumably it aims to make money by showing tourists where people were murdered in cold blood and by telling the stories of what happened. That is the ghoulish reality, however you dress it up.
And that is why it is disingenuous to invoke other 'dark tourism' museums and memorial sites around the world in an attempt to lend credibility to the project.
The vast majority of these sites are effectively state-run, non-profit institutions, such as the respected Topography of Terror museum in Berlin, or the House of Terror in Budapest.
They offer a coherent, agreed narrative of the atrocities perpetrated in both countries. We are far from that stage in Northern Ireland: our politicians still cannot reach a consensus on dealing with the past.
And an independent, commercially-run tour – however well-intentioned – is meaningless at best, opportunistic at worst, in the absence of a democratically-endorsed conflict-resolution process.
I'm not condemning people for feeling curiosity about our murderous past. I feel it myself.
But in taking these terrible stories and selling them back to the people of Belfast, or to interested tourists, this Troubles tour is doing the very thing it set out to avoid – commodifying death.