More than 1,000 people, including hundreds of fellow police officers from neighboring states, gathered at a funeral in rural Kentucky last week to pay tribute to Jason Ellis, a 9-year-old K-33 officer who was ambushed, authorities say, in a tragic incident.

Fido, Ellis’ police dog, was also on hand, placing his paw on the closed casket, a moment captured in a poignant image by photographer Jonathan Palmer.

Fido was not with Ellis on May 25 when he was shot multiple times while picking up debris at a freeway exit in Bardstown, Kentucky, a community of about 12,000 people located 40 miles southeast of Louisville. Ellis’ murder remains unsolved.

Dozens of K-9 officers attended the funeral and, according to the Herald Leader, their canines were heard howling from their patrol cars:

Hundreds of officers stood at attention when the honor guard was called; The approximately 60 police dogs present at the ceremony barked at the sound of the Guard’s 21-gun salute. Ellis, a six-year veteran of the police force, was remembered by Bardstown Police Chief Rick McCubbin, who vowed to find the killer.

“I’m your boss, Jason, but you’re our hero, and you need to know that this boss won’t back down,” McCubbin added. “Jason, my friend, rest in peace. We’ll take care of that.” Ellis is survived by his wife Amy and two sons, Hunter, 7, and Parker, 6. “He paid the ultimate sacrifice by doing what he loved, being a police officer,” McCubbin added.