Jesse Ryan Loskarn — who goes by his middle name — is expected to be arraigned on Thursday morning in federal court.

“Jesse Ryan Loskarn, 35, of Washington, D.C., was arrested this afternoon by the U.S. Postal Inspection Service based on probable cause for possession and distribution of child pornography charges,” a Justice Department spokesman said in a statement. “He remains in custody pending a court hearing that is expected to be scheduled for tomorrow at the federal courthouse in Washington, D.C.”

Postal Service agents searched Loskarn’s home earlier in the day, and then took him into custody. Loskarn’s computer in Alexander’s office was also searched, with the senator’s permission, Senate sources said.

Alexander, a Tennessee Republican, subsequently removed Loskarn from his office’s payroll and promoted longtime aide David Cleary to the chief of staff job.

“The courts will judge Mr. Loskarn’s guilt or innocence, but under these circumstances, he cannot continue to fulfill his duties as chief of staff of this office. Therefore, as of today, I have removed him from the payroll,” Alexander said Wednesday afternoon.

Loskarn was removed from his home in handcuffs by federal agents shortly before 1 p.m. on Wednesday and driven away in an unmarked car. Agents from the U.S. Postal Service were on the scene at Loskarn’s home in southeast Washington, D.C. in the Hill East neighborhood on a quiet, tree-lined block of rowhouses near the Stadium-Armory Metro station.

Loskarn did not respond to shouted questions from television reporters.

Agents put several bags of evidence and a computer in a postal inspector SUV. Agents also went to Alexander’s Senate office and sought access to Loskarn’s work computer, a Senate source said.

Loskarn is one of the most well-known Hill staffers and an influential policy aide. He is also very well-liked in the Senate, and the small community of those who work on the Hill was shocked by the news.

“I was just informed by the United States Senate legal counsel’s office that law enforcement agents are conducting a search of the personal residence of Ryan Loskarn, the chief of staff of my Washington, D.C., office regarding allegations involving child pornography,” Alexander said in an initial statement. “I am stunned, surprised and disappointed by what I have learned.

Priscilla Carver, a witness who lives just a few dozen feet from Loskarn’s home, said seven agents arrived right before 7 a.m. banging on the door and yelling. They arrived in four unmarked cars, and the home was sealed off by police tape. Agents left the area a few minutes after 1 p.m. Wednesday.

Loskarn is from Sykesville, Md., according to the congressional staffing database LegiStorm. He graduated from Tulane University in 2000 and has been working on Capitol Hill for Republicans ever since, according to his LinkedIn page.

A longtime Alexander aide, Loskarn was named his chief of staff in 2012.

Including working at the Senate Republican Conference under Alexander and former Sen. Jon Kyl (R-Ariz.) as both chief of staff and communications director, Loskarn also worked for Reps. Wally Herger (R-Calif.) and Marsha Blackburn (R-Tenn.), as well as the House Rules Committee.