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A truck driver plowed through a crowd at a Berlin Christmas market Monday evening, killing the passenger of the truck and eight others, Dec. 19, 2016. Pictured: The truck was photographed near the Christmas market at the city's center. Reuters

UPDATED: 4:40 PM EST — The Islamic State militant group has claimed responsibility for the truck attack in Berlin. The terror group called the assailant, whose identity remained unknown, a "soldier," according to the New York Times. It did not provide evidence to substantiate its claims.

UPDATED: 1:30 PM EST — Police have released the suspect taken into custody Monday at the Breitscheidplatz public square due to insufficient evidence. The man made a lengthy statement during a police hearing but denied that he was the driver. Police also found it impossible to prove that the man was in the truck's front cab at the time, or link him to witness testimony, according to Reuters.

Original story:

The person arrested for suspicion of "deliberately" ramming a truck into a crowd at a Berlin Christmas market was likely not the driver, local authorities announced Tuesday. Instead, the driver from Monday's suspected terror attack, which killed 12 people and injured 48 more, was still at large and possibly armed, officials said. Police warned people to remain "particularly alert."

It remained to be determined whether the person in custody, a Pakistani national, was the actual driver by later Tuesday, Germany's chief prosecutor Peter Frank said in a press conference. "We must get used to the idea that he was possibly not the perpetrator," he added.

German police raided a refugee shelter at a defunct airport early Tuesday morning arresting the "suspicious person" around 9:30 p.m. Monday local time at Breitscheidplatz, near the Christmas market. Officials later said the suspect denied having any role in the attack. It was not immediately clear whether he had been released.

Here's a list of everything we know so far about the unnamed assailant.

What The Suspect Did

The attacker's truck plowed through the Christmas market at city’s center, just across from the Kaiser Wilhelm Memorial Church. Along with wrecking the front of the vehicle, the suspect damaged sellers' stalls and tables.

Who Was With The Suspect?

The person in the passenger seat of the truck—the windows of which were smashed—was likely the incident's first victim, Berlin police said. Later, the AP reported that the man in the passenger seat, 37-year-old trucking company employee Lukasz Urban, was, as the man asked to identify Urban said, clearly "fighting for his life." The owner of the Polish trucking company said he believed Urban "would not give up the vehicle and would defend it to the end if it were attacked," according to the newswire.

Authorities told Reuters that Urban had been discovered with a fatal gunshot wound, but that no weapon had been found on the scene.

How German Authorities Are Characterizing The Act

The incident, which German authorities were investigating as an act of terrorism, will be handled by federal police and prosecutors. The violence immediately brought many back to a similar event in Nice, a city on France’s southern coast, where 31-year-old Tunisian truck driver Mohamed Lahouaiej-Bouhel drove straight into a dense crowd of people watching Bastille Day fireworks on July 14, killing at least 85 people and injuring hundreds of others.

(Lack Of) Affiliation With ISIS

While some, like the New York Post and the Sun, reported that the Islamic State terrorist group had claimed the attack as one of their own, Rita Katz, director of the SITE Intelligence Group, which monitors terrorist activities online, said otherwise.

Nationality

The arrest of a 23-year-old Pakistani man near the scene spurred finger-pointing at migrants seeking refuge in Europe from war-torn nations. However, the police confirmed that they had arrested the wrong person. Many were quick to blame Chancellor Angela Merkel for her relatively liberal policies on welcoming refugees into Germany.

Merkel herself said early Tuesday the attack "would be particularly repugnant in the face of the many, many Germans who have dedicated themselves day after day to helping refugees, and in the face of the many people who actually need our protection and try to integrate into our country," the Guardian reported.

Still, in a move that appeared to vindicate critics of her past immigration policies, German police raided a former Berlin airport, now a shelter for refugees, early Tuesday morning, Reuters reported. Authorities told German media the suspect was likely from Afghanistan or Pakistan and had entered Germany a year earlier, according to the newswire.