Howard Liebengood, an off-duty United States Capitol Police officer and 15-year veteran who responded to Wednesday’s violent riots, has died. He was 51.

The United States Capitol Police (USCP) confirmed Liebengood’s death in astatementon Sunday morning. A cause of death was not immediately disclosed.

According to the USCP union, Liebengood, who joined the law enforcement agency in 2005 and was assigned to the Senate Division, “was among the officers who responded to the rioting at the U.S. Capitol on January 6th.”

“We extend our deepest sympathies to Officer Liebengood’s family and we mourn the death of a friend and colleague who worked alongside us to protect the lives of the Members of Congress, their staff and all who serve at the U.S. Capitol,” the union’sstatementread.

“We pay tribute to his service and we grieve for the loss of a fellow officer,” the statement added.

The USCP has not responded to PEOPLE’s request for additional information.

Howard Liebengood.Tom Williams/Roll Call/Getty Images

Howard Liebengood

Liebengood is the second officer to die after the Capitol riot, in which a large group of pro-Trump supporters stormed the Capitol building as lawmakers gathered to certify Electoral College votes for President-electJoe Biden.

Officer Brian D. Sicknick, 42, died at 9:30 p.m. Thursday from injuries he sustained “while physically engaging with protesters” during the rampage, the USCP said in a previous statement.

“He was a great guy to work with,” a colleague of Sicknick, who did not wish to be identified, told PEOPLE. “You knew you could count on him to do his job and be right there when you needed him. He believed in this country and he believed in all of us [who worked with him].”

Officer Brian D. Sicknick.USCP

United States Capitol Police Officer Brian D. Sicknick

According to the Capitol Police, over 50 officers from the department and Metropolitan Police Department sustained injuries, while several requiring hospitalization.

“The violent attack on the U.S. Capitol was unlike any I have ever experienced in my 30 years in law enforcement here in Washington, D.C.,” Capitol Police Chief Steven Sund, who resigned from his post on Thursday, said in a previous statement. “Make no mistake – these mass riots were not First Amendment activities; they were criminal riotous behavior.”

source: people.com