A hacker exploited a vulnerability in a Maricopa County, Arizona, website and obtained more than 600,000 voter registration files shortly before the 2020 election, according to newly declassified FBI and intelligence community records released Thursday.

The FBI eventually identified the alleged hacker, searched his Arizona home, and obtained an admission that he had written a computer script to exploit the vulnerability, the records show. But federal, state, and local prosecutors declined to bring charges, and the FBI ultimately closed the investigation in 2023.