The echo of the black-clad gunman's bullets on such a globally festive night will reverberate long and hard.
The year 2016 had already laid a terrible and bloody foundation of terrorist mayhem for Turkey's citizens: Dozens of attacks, from Europe's easternmost tip in Istanbul through to Turkey's southern border with Syria.
At times last year it felt that barely a week went by between strikes, from a brazen gun and bomb raid at Istanbul's main international airport to carnage on the city's tourist-filled streets, to the assassination of Russia's ambassador in the capital, Ankara, 12 days ago.
Such was the crescendo of attacks in the last few months of 2016 that the terror at Reina nightclub had a feeling of inevitability about it -- if not there precisely, then someplace similar: upmarket, secular, serving alcohol.
Barely two months ago, the US State Department warned that "extremist groups are continuing aggressive efforts to attack US citizens in areas of Istanbul where they reside or frequent."
In a year, Turkey has gone from popular tourist destination to disturbingly dependable terror venue. That's not a reputation any country wants -- and particularly not Turkey, with its economy struggling following an attempted coup last summer. This has not come out of nowhere.
Decades of bloody conflict
There are two brands of terror targeting Turkey now: Kurdish and radical Islamist.
It would be easy to lay the blame for the growth of both at the feet of Turkey's increasingly autocratic and powerful President Recep Tayyip Erdogan, but that would be to oversimplify the upheaval underway in this once secular country.
Yet Erdogan shapes Turkey's destiny more than any other single person.
Four years ago he ended three decades of bloody conflict with the country's Kurds. They make up one fifth of Turkey's 80 million people. Tens of thousands died in a terror campaign as they fought the state for better rights.
With peace came popularity, a secular Kurdish party winning seats in the following national elections. But their gains threatened Erdogan's grip on parliamentary power.
As this was playing out, the war in neighboring Syria was heating up. The United States did a deal with Turkey to use its Incirlik airbase close to the Syrian border in order to strike ISIS targets. In return, Turkey agreed to strike "terrorists" too.
But when Turkey did, its focus wasn't ISIS, but its old foe the Kurds, whom, it was feared, were gaining ground inside Syria.
Within months, Turkey's war with the Kurds was back on; snap elections a few months later crippled the Kurdish vote and restored Erdogan's party's hold on government.
By 2016, Kurdish tit-for-tat bombings, ambushes and gun attacks -- mostly against military and police targets -- had become the ugly background music of the year.
Transit point for ISIS recruits
To that already monstrous din, ISIS has added its own sordid battle noise.
Like the renewed conflict with the Kurds, this too has its roots in Syria, and once again President Erdogan played a leading role in shaping its course.
In the early years of the Syrian uprising, Erdogan sought to unseat his onetime friend President Bashar al-Assad by backing Sunni rebels.
Unlike the US and Europe, Erdogan didn't seem so picky about who benefited from his largesse, often choosing conservative Islamist rebels, rather than moderates.
As ISIS grew in strength, they profited from Turkey's policy toward rebels. Thousands upon thousands of ISIS recruits transited Turkey on their way to the war.
Near-open borders allowed ISIS fighters and their weapons to pour across, and most damaging for Erdogan, resupply hubs, escape routes and safe houses to develop right under his nose.
Before the country belatedly tightened its border security, Turkey became riddled with ISIS.
As the war in Syria morphed and Russia moved in to save Assad, Erdogan began to reassess. With the US an ineffective partner in the war -- for his aims at least -- the Turkish leader turned to the increasingly influential Vladimir Putin in Moscow to cut a deal.
The assassination of the Russian ambassador by a Turkish policeman in Ankara
the week before Christmas highlighted how swift an about-face Erdogan has executed. Few Turks expected his support of their co-religionists, the Sunni rebels, to wither so fast.
Turkey in the crosshairs
It is clear however, that ISIS saw the writing on the wall. Turkey was transitioning from benign conduit to outright enemy.
They didn't immediately claim responsibility for the July attack on Ataturk airport, but by the end of the end of the year the gloves were off.
In recent weeks, pro-ISIS groups had called for attacks in Turkey
, urging lone wolf assaults on clubs, markets and movie theaters over the holiday season to turn them in to days of "terror and blood."
Neither ISIS nor the Kurds have any reason to scale back their assault, and Turkey is well and truly in their crosshairs.
The Kurds will focus on military and police targets, civilian collateral an accepted part of their terror package.
ISIS will gravitate towards westerners and to undermining the Turkish state. They'll target tourists to hit the economy, and wage open war on Turkey's secularists to rive at the wound Erdogan has already opened between conservatives and the less religious.
ISIS' aim will be to create chaos, the Kurds' to continue a generational fight. Neither bodes well for Turkey, its neighbors in Europe or its allies in Washington.
It's clear that 2016 killed the status quo, and 2017 is already a dark canvas.