It's not immediately clear from the statement whether the activities that led to the arrest involved more than just contributing to the Tornado Cash codebase, but it would be very concerning if not. There are complexities around the sanctioning of Tornado Cash — a fairly decentralized software project — that raise concerns about the criminalization of code. For many, it brings to mind the "Crypto Wars" (where "crypto" is referring to cryptography rather than cryptocurrency).
A suspected developer of the Tornado Cash cryptocurrency tumbler was arrested in the Netherlands, according to the country's Fiscal Information and Investigation Service (FIOD). They said that he was "suspected of involvement in concealing criminal financial flows and facilitating money laundering". Wallet addresses used by Tornado Cash were sanctioned by the United States several days prior due to their use in laundering the proceeds of criminal activities.