Authorities arrested the UK security researcher known for stopping the WannaCry ransomware attack in May.

On Wednesday, 22-year-old Marcus Hutchins — who runs a security blog called MalwareTech — was arrested in Las Vegas for “his role in creating and distributing the Kronos banking Trojan,” according to a spokesperson from the U.S. Department of Justice.

The charges relate to alleged conduct occurring between July 2014 and July 2015.