The mastermind of Tuesday’s Istanbul airport massacre appears to be a one-armed Chechen terrorist who trained Russian-speaking militants, had a long history of supporting terror and was known as “Akhmed One-Arm,” according to several government documents and regional media reports.

Akhmed Chatayev was identified by the pro-government Yeni Safak newspaper as the organizer of the coordinated assault, which killed 44 and wounded more than 200 others at Turkey’s Ataturk Airport. Turkish officials did not immediately confirm he was involved in the attack, and it was unclear if Chatayev was one of the airport bombers, in custody or on the run.

Authorities said all information suggested the airport assault was the work of ISIS and, despite no claim of responsibility for the attack, Chatayev’s involvement would show an ISIS link.

Chatayev had been designated in October as a terrorist by both the U.S. Treasury Department and UN Security Council for supporting ISIS. The Treasury report identified Chatayev as a member of “a group of militants that was planning attacks against U.S. and Turkish facilities” and the UN report said Chatayev “directly commands 130 militants” and was the “organizer and mastermind of planned” terror acts against Russian interests abroad.

He’s described as appearing in numerous videos in 2014 and 2015 in which he associated with other members of ISIS and greeted extremists in Dagestan.

Chatayev began his extremist activities as a Chechen rebel fighting the Russians in the mid-to-late 1990s, according to numerous news organizations in the region. He was allegedly wounded in battle and captured, winding up in a Russian prison where he claimed he was brutally tortured. It’s during this time Chatayev is believed to have lost the lower portion of his right arm, though it’s unclear if it was cut off for punishment or amputated for medical reasons.

He left Chechnya in 2001 for Austria, where he provided support to Chechen rebels, including a September 2007 delivery of money and military uniforms, according to the UN terror listing. Chatayev was given refugee status during his time in Austria, The Georgian Journal reported. He spent time in a Swedish prison in 2008, according to the Journal, and was later apprehended in the Ukraine. It was expected he would be extradited to Russia, where he was wanted by authorities, but Chatayev was instead extradited to Georgia, the Journal reported.

In August 2012 he was involved in the Lopota Gorge incident in which militants took several people hostage and killed three members of Georgia’s security forces. Chatayev proclaimed his innocence and said he was merely a negotiator. He was cleared of all charges stemming from the incident by a Georgia court in January 2013, however.

Turkish police on Thursday linked the airport suicide bombers to Russia, Uzbekistan and Kyrgyzstan, with Osman Vadinov, from Chechnya, named as one by Turkey’s Hurriyet newspaper. Vadinov reportedly arrived in Turkey in 2015 from Raqqa, the Syrian capital of ISIS’ so-called caliphate.

Vadinov and Chatayev may only be the most recent terrorists to come out of the Northern Caucuses region. The brothers who perpetrated the Boston Marathon bombing in April 2013, Dzhokhar and Tamerlan Tsarnaev, lived in Dagestan, a territory close to Chechnya, and the brothers' father was Chechen.

Additionally, Tamerlan Tsarnaev travelled to Dagestan prior to the attack and was thought to be seeking ties to the group Caucasus Emirate. Chatayev was known to be a high-ranking member of that group before he joined ISIS.

Authorities also rounded up 13 suspects in connection with the attack after raids in Istanbul's Pendik, Basaksehir and Sultanbeyli neighborhoods, Anadolu Agency reported.

Police seized three hunting rifles and documents relating to ISIS.