The first white British man has been publicly identified as joining ISIS in Syria, according to The Sunday Times.

The paper reports that Jack Letts, a 20-year-old man originally from Oxford, joined the radical Islamist group and secretly traveled to Syria two years ago.

Letts apparently converted to Islam while living in Oxford, and attended the Madina Masjid mosque in the city.

He comes from a non-Islamic background: His family is reportedly secular, his father working as an organic farmer and archaeobotanist, and his mother as a books editor. He studied at Cherwell school, supported Liverpool football club, and allegedly drank alcohol and smoked cannabis before his conversion.

Letts was reportedly nicknamed "Jihadi Jack" by his peers in Oxford.

The moniker mirrors "Jihadi John," another high-profile British Islamic State militant. The former Londoner, really named Mohammed Emwazi, became infamous after appearing in ISIS execution videos of Western journalists and aid workers including James Foley and Steven Sotloff. Emwazi was killed in a drone strike in November 2015.

Jack Letts now apparently uses the name Abu Muhammed, and married a woman from Fallujah in Iraq after he came to Syria. The Daily Mail reports he has a son, named Muhammed. He is apparently a frontline fighter, and lives in the Syrian city Raqqa.

A photo that The Daily Mail reports shows the interior of Letts' home in Raqqa. The Daily Mail

He reportedly first traveled to Syria after telling his parents he was going to study Arabic in Kuwait. According to The Sunday Times, Letts revealed to his parents the truth in September 2014. A source to "close to his family" told the paper: "His mother and father were extremely worried for his safety after he told them that he was in Syria. The past two years have been a real nightmare for them. They just wish he can be back home with them."

The Daily Mail and The Sunday Times have both seen photos Letts posted to social media apparently showing him in Syria. A Facebook profile for a "Jack Letts" from Oxford that shows photos that The Daily Mail reports are of Letts has its profile picture set of a smoke cloud from an apparent explosion seen from a roof in what seems to be a Middle Eastern setting. In a comment from May 2015, Letts says he is "travelling."

According to The BBC, more than 700 people have traveled from Britain to Syria and Iraq to support jihadist groups — mostly ISIS, also known as Islamic State.