Family members of the six fallen heroes from the past year, including Nicholson, were in attendance, as were family members of first responders who have died in past years.
Friday's event was the 23rd annual ceremony at the memorial gardens.
Highbarger and Larry Nicholson accepted a bronze plaque that is a replica of the Fallen Heroes Memorial at the Memorial Gardens.
Nicholson was a well-known and respected officer, a person the Smithsburg townspeople turned to when they had problems, said Mary Beth Marsden, an ABC Channel 2 anchor who emceed the event.
Gov. Martin O'Malley issued a proclamation declaring May 2 as 2008 Fallen Heroes Day in Maryland. He also ordered flags flown at half-staff.
Surviving family members of another local fallen hero were recognized.
O'Malley gave a proclamation to three sisters of late Maryland State Police Trooper 1st Class Lauren Ridge on behalf of the families of fallen police officers throughout the state. Ridge was shot and killed in 1950, the only trooper stationed at the Hagerstown barracks killed in the line of duty, police have said.
O'Malley kissed each of the women on the cheek as he presented the proclamation.
Baseball Hall of Famer Brooks Robinson, a former Baltimore Orioles third baseman, gave the memorial address.
His father was a firefighter. As he was growing up, his father and his father's firefighter friends were his heroes, Robinson said.
"I hope our recognition of your loss comforts you in some small way," he said. Taking a phrase he once saw at Memorial Stadium in Baltimore, Robinson ended his address by saying, "time will not dim the glory of their deeds."
O'Malley called first responders "our defenders" who put their lives on the line so everyone else can sleep at night knowing their families are safe.
The governor thanked the families for the "tremendous sacrifice" they made, although he acknowledged no one can ever make the hurt go away.
During a song entitled "Be My Angel," Nicholson's fiance, Desiree Grimes, burst into tears. His mother and brother, Ryan Nicholson, also dabbed at their eyes with tissues.
"I can't say that I've moved on, that will take some time," Grimes said after the ceremony. "He was a wonderful person, there will never be another one like him."
At the conclusion of the ceremony, the Easton Police Department rifle team gave a rifle salute and six law enforcement helicopters flew over the memorial gardens.
Douglas Pryor faces first-degree murder charges in Nicholson's death and the death of Pryor's estranged girlfriend, Alison Munson. He faces the death penalty if convicted.
Pryor is scheduled to appear in Washington County Circuit Court May 20.