Anis Amri

Six individuals including some friends of Amri's were arrested on 8 April 2018 for planning a knife attack on a sports event in Berlin. The main suspect was under police surveillance. They were all released after no evidence was found that they were planning a terror attack.

In preparation for the Christmas market 2018, the Breitscheidplatz square and its surrounding were fortified against further terrorist attacks.

On 28 December, German prosecutors said they had detained a 40-year-old Tunisian man, who they thought may have been involved in the attack. Amri had saved the number of this man in his phone. Prosecutors stated on the next day that he was released after investigations revealed that he was not a suspected contact of Amri. They also confirmed that the attacker had sent a mobile phone voice message and a picture to a contact shortly before carrying out the attack. The German police raided the homes of two suspected associates on 3 January 2017, including a 26-year-old Tunisian man they suspected of being in contact with Amri and knowing about the attack as well as a former flatmate of Amri. The Tunisian suspect who was suspected of either planning the attack or knowing about it was detained with federal prosecutors stating that he had known Amri since the end of 2015, had met him a day before the attack and both had "very intense conversations". Amri's former flatmate was also being investigated and the attacker had tried to contact him twice on 19 December.

On 17 May 2017 the Interior Ministry of Berlin stated that already in November 2016 intelligence was given that Anis Amri was involved in criminal offenses concerning drug trafficking. On this basis authorities would have been able to apprehend Amri already at the time, however they did not. An investigation was launched trying to find out to what extent these informations were withheld by the State Criminal Police Office of Berlin after the attack happened. Several days later, while the investigation for obstruction of justice was still going on, a speaker of the Interior Ministry said that manipulations of the file of Amri have been carried out by officers of the criminal investigation department after the attack. On 22 May 2017 a commission of inquiry was initiated starting in July. Meanwhile, a special prosecutor was appointed to the case. In addition to the ongoing investigation concerning manipulations of the file and withholding of information, national TV reported on 1 June, that officers who were ordered by an investigating judge in Berlin to observe Amri until October 2016 for criminal offenses and possible terrorist links did not do so and instead included untrue records regarding observing actions in his file.

A petition to award Urban the Bundesverdienstkreuz had gathered over 2,500 signatures by the afternoon of 22 December. A donation page to support his family was set up on GoFundMe and collected more than £110,000 by 23 December by British truck driver Dave Duncan. He was officially thanked by Polish Ambassador to the United Kingdom Arkady Rzegocki at a ceremony at Embassy of Poland, London on 9 January 2017. Polish authorities provided funds for the delivery of Urban to his family as well as the costs of the funeral and the family of Urban received a state pension. German authorities refused to reimburse the value of the destroyed truck which belonged to a company run by Urban's cousin.

In February 2017, the German Salafist mosque organisation Berliner Fussilet-Moscheeverein was banned by authorities. Amri was said to be among its visitors. In March 2017, the German Muslim community organisation Deutschsprachige Islamkreis Hildesheim was also banned after investigators found that its members were preparing to travel to the conflict zone in Syria to fight for the Islamic State. According to the Federal Agency for Civic Education, these examples show that Salafist mosques not only concern themselves with religious matters, but also prepare serious crimes and terrorist activities.

On 19 December 2016, a truck was deliberately driven into the Christmas market next to the Kaiser Wilhelm Memorial Church at Breitscheidplatz in Berlin, leaving 12 people dead and 56 others injured. One of the victims was the truck's original driver, Łukasz Urban, who was found shot dead in the passenger seat. The truck was eventually stopped by its automatic brakes. The perpetrator was Anis Amri, a Tunisian failed asylum seeker. Four days after the attack, he was killed in a shootout with police near Milan in Italy. An initial suspect was arrested and later released due to lack of evidence.

The Berlin attack took place during a time of heightened Islamist terrorist activity in Europe. Several terrorist attacks in 2016, in Germany and in neighboring countries, have been linked to ISIS; some of them were similar to the truck attack on the Christmas market in Berlin (e.g. the 2014 Nantes attack and the 2016 Nice truck attack).

On 19 December 2016, at 20:02 local time, the perpetrator drove the stolen truck through a Christmas market at Breitscheidplatz in the City West of Berlin, killing 11 people and injuring 56. The incident is the deadliest terrorist attack in Germany since an attack at Oktoberfest in Munich in 1980, which killed 13 people and injured 211 others. The truck came from the direction of Hardenbergstraße, drove about 50 metres (160 ft) through the market, and destroyed several stalls before turning back onto Budapester Straße and coming to a stop level with the Kaiser Wilhelm Memorial Church.

The German government reformed its security rules in response to the attack. Among the proposals in the anti-terror plan were easing the deportations of rejected asylum seekers, increasing surveillance of those to be deported and those considered to be terror risks, limiting movement of some asylum seekers within Germany, using electronic tags on those deemed terror threats without a trial, lengthening the period suspects can be held in custody and limiting development aid to countries that don't cooperate in deportation processes. President of Tunisia Beji Caid Essebsi meanwhile stated that Europe "must be calm", vowing to take responsibility for the attacks, but insisted that it was necessary to verify citizenship before accepting deportations. The Bundestag passed a new surveillance law on 9 March in response to the attack as well as other attacks that occurred in Germany in 2016. The law gives priority to public safety when deciding on whether to permit installation of video surveillance in some locations and makes it easier for private companies to install these systems in public places. It also voted for allowing the Federal Police to install surveillance systems for reading and registering licence plate numbers.

In Tunisia, Amri was sentenced in absentia to five years in prison, "reportedly for aggravated theft with violence". Prior to that he had been arrested several times for possession and use of drugs. According to his family, he drank alcohol, took drugs and was initially not religious, but had been radicalized in Italian jails. The man arrived in Germany in July 2015 and applied for asylum in April 2016. He used at least 14 different aliases and posed as a citizen of Syria, Egypt or Lebanon. He reportedly had tried to recruit participants for a terrorist attack since the spring, and once tried to buy a pistol from an undercover police officer. He had been overheard by the German intelligence offering to carry out a suicide attack, but the German authorities had decided not to arrest him because they deemed him a mere errand boy. The German CID warned in March 2016 that he was planning a suicide attack and recommended immediate deportation. However, the state government of North Rhine-Westphalia ruled he could not be deported. In Germany he was involved in a bar brawl and drug dealing; later he was involved in a knife attack over drugs in July 2016 and disappeared after police tried to question him. Three weeks before the attack, Moroccan intelligence warned Germany about the terrorist attack planned by him. He had started spending more time in Berlin before the attack and was being closely monitored, however showed no signs of planning a terrorist attack per a report submitted by the German Interior Minister to the state parliament of North Rhine-Westphalia. German authorities were seeking to deport him at the time of the attack, however the legal requirements hadn't been met because Tunisia initially denied that Amri was their citizen but documents confirming it arrived in Germany after the attack.

Amri fled from Tunisia to escape imprisonment for stealing a truck and arrived for the first time in Europe in 2011 on a refugee raft at the island of Lampedusa. He lied about his age, pretending to be a minor, and was sent to the temporary migrants reception center on the island. At the center, according to Italian security officials, Amri "took part in a particularly violent riot, when the center was set on fire and several people were injured" and was sentenced for it and robbery to four years in prison, which he served in two jails in Sicily. Amri was released in 2015; according to Italian officials, the Tunisian authorities refused to accept his repatriation to Tunisia, and it is believed that he went to Germany around this time. Per an autopsy on his body, it was found that he frequently consumed drugs.

On 21 November, the United States Department of State warned that Americans "should exercise caution at holiday festivals, events, and outdoor markets" throughout Europe. This was in view of the threat from ISIL, Al-Qaeda and affiliated groups, including self-radicalized extremists. Going back to at least 2000, a Frankfurt-based Al-Qaeda plot to bomb the Strasbourg Christmas market was foiled by law enforcement.

On 21 December, police announced that investigators had found, under the truck's driver's seat, a suspension of deportation permit belonging to Anis Amri, a man who was born in Tataouine, Tunisia, on 22 December 1992. Authorities began a Europe-wide search for Amri. According to investigators, Amri entered Germany from Italy in 2015 and had contacts with the network of the recently arrested Salafist preacher Abu Walaa, a known ISIL recruiter in Germany. Amri was sought by the Federal Criminal Police Office. Officials called for a public manhunt, issuing a recent picture, and offering a reward of €100,000, warning that Amri might be armed and dangerous. He was described as being 178 cm (5 ft 10 in) tall, weighing approximately 75 kilograms (165 lb), with dark hair and brown eyes.

Italian police confirmed on 4 January that the gun used in the attack, a .22-caliber Erma Model EP552S pistol (Walther PPK clone), matched the one found on Amri. ZDF reported on 6 January that he might have acquired the gun in Switzerland and lived there for a prolonged period of time whose length investigators were trying to determine. Swiss prosecutors meanwhile opened a case related to the attack. The Office of the Attorney General of Switzerland later confirmed that he had spent some time in the country while the German police were investigating whether the gun was acquired by him there. Investigators stated on 18 January that the gun was imported legally into Switzerland in 1990s, but it remained unclear what happened to it afterwards as it didn't appear in the weapons registers of cantons of Switzerland and there was no national weapons register at the time.