ISIS claimed responsibility for Monday’s Christmas market slaughter not long after German authorities released their initial suspect.

By Katie Zavadski –  12.21.16  – THE DAILY BEAST – A “soldier” of the Islamic State carried out the truck attack in Berlin on Monday evening, the terrorist group claimed through its unofficial news agency. Twelve people were killed and dozens more injured when a hijacked truck loaded with steel crashed into a popular Christmas market. A suspect was detained near the scene by German authorities, but he was later released on Tuesday, when officials said they did not have proof he was the individual driving the truck.

The claim of responsibility comes through the Amaq News Agency, which ISIS typically uses to announce attacks it orchestrated or inspired. Like in other claims of responsibility, the news agency cited a security source within the Islamic State. It is not immediately clear whether the terrorist group directed or merely inspired the perpetrator of the Berlin attack.

Amaq does not typically provide proof of ISIS involvement in attacks, but it has a history of being careful about which foreign attacks it claims. While ISIS supporters celebrated when a German-Iranian teenager opened fire inside a Munich shopping mall in July, ISIS did not formally claim that attack. The teen was later revealed to have had psychiatric problems and no ties to ISIS. Amaq sometimes later posts video pledges of allegiance from perpetrators of attacks it claimed, and other times, the perpetrators are later linked to ISIS by authorities.

German authorities have not identified the individual responsible for the Monday attack and said that the armed perpetrator is likely still on the run. An asylum-seeker from Pakistan was detained near the site of the attack on Monday evening. But the man, identified only as 23-year-old Naved B, was released on Tuesday, and the federal prosecutor’s office said that “forensic tests carried out so far” did not link the man to the crime. According to The Guardian, an eyewitness saw a man exit the cab of the truck and offered police a description. Naved was later detained because he appeared to match it. Earlier reports mistakenly said the eyewitness had followed the suspect from the attack site.

The Berlin truck attack claim is somewhat unusual in that ISIS does not typically claim responsibility for attacks where perpetrators are still at large, or have been apprehended by authorities. On Tuesday, CNN reported that the suspect in a planned attack on a high-speed train in France last year confessed—but only after his links to Paris attacks ringleader Abdelhamid Abaaoud were disclosed in an academic journal. He had previously said the attack was motivated by hunger, and ISIS did not claim it, even though the man allegedly had deep ties to established leaders. (The attack was thwarted by two vacationing American servicemembers and their friend.) Likewise, the terrorist group has not claimed Ahmad Rahimi, who allegedly placed bombs at various locations in New York and New Jersey this summer, even though authorities have discovered writings that appear to show his affinity for the terrorist group.

This is the third vehicular attack in the West claimed by ISIS in the past year, and comes on the heels of an issue of its propaganda magazine calling on supporters in the West to carry out such attacks. As was the case in an attack at Ohio State last month, the Berlin attacker evidently carried a knife to cause additional damage after the vehicle stalled. The Polish truck driver, who was found dead inside the truck, had bullet and stab wounds.

Both vehicular and knife attacks were heavily encouraged by ISIS propaganda magazine Rumiyah in recent issues. The new focus on Rumiyah, or Rome, appears to indicate a shift in the terror group’s focus from Dabiq, the Syrian town where they expected to triumph against other forces. (It lost Dabiq to opposition forces this year.)

In the second issue of the magazine, ISIS published a detailed guide on choosing a knife and approaching a knife attack. The message was then reinforced by a video of knife attack instructions published by the terror group. The third issue followed up with instructions on how to conduct a vehicular attack and how to choose the truck. It suggested outdoor markets as one of the possible targets and having a secondary weapon—such as a gun or knife—to maximize damage.