A former Capitol Hill staffer accused of doxxing Senators during the Brett Kavanaugh nomination hearings pleaded guilty Friday to five charges, including witness tampering and computer fraud.

Jackson A. Cosko, 27, of Washington, D.C., pleaded guilty in federal court to two counts of making public restricted personal information; one count of computer fraud; one count of witness tampering, and one count of obstruction of justice. Cosko posted the cell phone numbers and home addresses of senators onto the web from House and Senate computer networks.

In documents submitted as part of today’s plea, Cosko admitted that he was angry about being fired in May 2018 as a systems administrator in Sen. Maggie Hassan’s office. Between July and October 2018, he “engaged in an extensive computer fraud and data theft scheme,” according to a statement from Alessio D. Evangelista, the Acting U.S. Attorney in this case, and Matthew Verderosa, Chief of the U.S. Capitol Police.

Cosko could face more than two years in prison. His plea agreement requires him to forfeit computers, cellphones and other equipment used in the crimes.

Sentencing is set for June 13, 2019.

“Doxxing” is the act of gathering personal information about someone — by legal and illegal means — and posting that information online.

An October 2018 affidavit from Capitol Police Capt. Jason Bell alleges that on Oct. 2, staff from Hassan’s office called police after they witnessed Cosko enter the senator’s office and use a computer. Cosko, a former Hassan staffer, did not have “permission or authorization” to be in Hassan’s office that night.

Cosko admitted to breaking into Hassan’s office on at least four instances and accessing Senate-network computers to steal information, including the contact information for other senators.

Hassan staffers confronted Cosko, and after he typed a few more things he left the office, the affidavit said. 

Witnesses from Hassan’s staff said the computer was logged in to a staffer’s account, and a program they had never used was running. Later that night, a Hassan staffer, identified as “Witness 2” in the court documents, received a threatening email from livefreeorpwn@gmail.com, with the subject line “I own EVERYTHING.”

“If you tell anyone I will leak it all. Emails signal conversations gmails. Senators children’s health information and socials,” read the email.

Cosko was behind the release of Majority Leader Mitch McConnell’s home addresses in Kentucky and Washington D.C., by adding them to a public Wikipedia page.

The information was picked up by the @congressedits Twitter account, which automatically broadcasts Wikipedia changes from Capitol IP addresses to thousands of followers. Twitter suspended that account in October 2018, after the doxxed information was posted in their feed.

Posting personal information “is considered one of the most serious violations of the Twitter Rules,” according to the social media company’s website.

During the Senate Judiciary Committee hearing with Supreme Court nominee Brett Kavanaugh and sexual assault accuser Christine Blasey Ford, the personal home addresses, home and cell phone numbers, and email addresses of GOP committee members Lindsey Graham, Orrin G. Hatch and Mike Lee were added to their public Wikipedia pages.

The Capitol Police determined the IP addresses used to edit the Wikipedia pages during the hearing were tied to the House, and the later release of McConnell’s info was done from a Senate network. Investigators eventually tracked down the digital trails to Cosko.