Charleston Hartfield, 34 and a married father-of-two, was off duty and attending the big country music festival that became a shooting range for retired accountant Stephen Paddock as he attacked with high-power rifles from a 32nd-floor hotel room.
As a cop, Officer Hartfield had been assigned to a conflict prevention task force in the southeast of the city.
He had just published a book about his life in the police force, which he joined in 2011.
Officer Hartfield was a military veteran who also coached football.
Several colleagues took to the podium at the memorial ceremony held beside a monument to fallen officers at the city's police academy.
"No one really planned to say goodbye to Charlie so soon," Steve Grammas of the local police union said.
Jake Grunwald, who graduated from the police academy with Officer Hartfield, choked back tears as he said the late officer "made us strong, our platoon" when it came to enduring the tough training regime at the academy.
The night of the shooting, when Officer Hartfield failed to answer phone text messages, colleagues thought it was because he was helping wounded people. Then they learned he was among the dead.
Nearly 500 people were wounded in Paddock's shooting rampage. His motive remains unknown.
