The families of four late U.S. Capitol Police officers were welcomed at the agency’s annual memorial service Monday.

The service, held at the U.S. Capitol, honored officer Jacob Chestnut and detective John M. Gibson, who were both shot and killed after a gunman opened fire inside the Capitol on July 24, 1998. Sgt. Christopher Eney was also honored; he was accidentally shot and killed during a training exercise Aug. 24, 1984. And also, Sgt. Clinton Holtz, who suffered a medical emergency Jan. 17, 2014 and later died.

“I want the families to know that we’ll never forget,” said Chief Matthew Verderosa, who worked alongside three of the men.

He said Monday’s service was about honoring the work these officers had contributed to the police force and the sacrifice they made. [related_gallery align=”right”]

“We need heroes like that to remember what freedom is all about,” Verderosa said.

This memorial marks Verderosa’s last as chief as he prepares for retirement after serving for 34 years. He said it’s an honor to have known and served with officers willing to make the ultimate sacrifice.

The names of the officers are now inscribed on the National Law Enforcement Officers Memorial, a tribute honoring the lives of fallen law enforcement officials.