The recent terror attacks in cities like Nice, Brussels, Ankara, Orlando and Paris are fresh, as is the summer shooting in Munich. A certain tragic routine has been established of posting #jesuis[fill in the city] and changing your profile photo.

In the case of Berlin, the use of the similar #IchBinEinBerliner hashtag not only recalls the violent events of recent months, but also references a significant moment in Berlin's history.

On June 26, 1963, US President John F. Kennedy spoke those words - "I am a Berliner" - to a city that was caught in an enclave between East and West, divided down the middle and threatened by a Cold War that could have turned hot at any time. Just as in the present struggle against terror, Kennedy expressed his solidarity in a situation where the enemy and even the danger itself were abstract.

.

Some Twitter users posted illustrations to underline their condolences, though there were decidedly fewer than following recent attacks in France and Belgium. "Christmas magic falls apart and takes a couple of small lights with it," reads this tweet.

On July 14, a cargo truck was deliberately driven into crowds celebrating France's national holiday in Nice - an act of Islamist terror that took 86 lives. The city of Nice was also quick to tweet its solidarity with Berlin using the hashtag #IchBinEinBerliner: "The city of Nice and the people of Nice show solidarity with the people of Germany in the face of horror. All our thoughts are with the victims and their families."

The public square where the incident took place, Breitscheidplatz, is located in the heart of the German capital, near the Kurfürstendamm shopping boulevard and the Zoologischer Tiergarten park.

It's one of the busiest places in the city - and also a popular tourist destination. US band One Republic posted that they had visited the Christmas market at Breitscheidplatz the night before the attack. The band made an appearance on "The Voice of Germany" casting show over the weekend.

German celebrities also took to Twitter to express their shock, as well as their solidarity and encouragement for the rest of the country.

Rapper Jan Delay simply posted the equivalent of "Oh my God," or "Holy shit."

Jan Böhmermann, a German satirist who made headlines in recent months for offending Turkish President Erdogan in a video, wrote: "No fear. No hate. No fear. No hate. Let's stick together. Have a safe, good evening." Böhmermann canceled his performance together with comedian Olli Schulz Monday evening at Berlin's Tempodrom in light of the tragedy.

A German comedian who was also performing last night in Berlin was Oliver Kalkofe. He elaborated in a long post on Facebook why he decided to remain on stage following the tragedy, which he heard about during intermission. Any decision would be wrong at that moment, he wrote, but he chose to go on with the show, full of understanding for those who chose to leave under the circumstances.

On Monday, two other acts of violence made headlines: a shooting at a Muslim prayer center in Switzerland and the assassination of the Russian ambassador to Turkey. The weight of three crimes within the space of hours - particularly after the numerous tragedies that have taken place over the course of the year - was clearly felt.  

In addition, a number of users took to Twitter to quickly condemn the tragedy as a terrorist attack, although police have yet to confirm the motive. Many blamed German Chancellor Angela Merkel, even calling for her resignation in some cases.