On Nov. 30, Gerhart was at the church helping with the food ministry when a fire call came in for a house fire a few blocks away. He apparently fell off the firetruck and struck his head on the pavement while responding to the fire.
He was flown to York (Pa.) Hospital, where he died Sunday afternoon without having regained consciousness.
Rev. John Dromazos said that Gerhart's fellow firefighters displayed "unbelievable compassion as they stood vigil Tuesday to Sunday" with Gerhart's family.
Hundreds of uniformed firefighters from Washington, D.C., Howard County, Md., and other companies attended the service.
Gerhart began his fire service career as a member of the Junior Hose and Truck Co. No. 2 of Chambersburg. He held life membership in many local fire companies. During his 31-year career as a professional firefighter with Engine Co. No. 17 in Washington, D.C., Gerhart twice received the department's highest award, the Bronze Bar of Valor, along with many other awards and commendations.
James Martin, assistant fire chief with the District of Columbia Fire Department, served with Gerhart for many years.
"Jack was one of an elite group of technicians," Martin said. "Others called him before making changes to the apparatus. He knew his job extraordinarily well. The department is a better place because of him."
Martin expressed his condolences to Gerhart's widow, Patricia Gerhart; mother, Janet Gerhart; and daughter, Susan Gerhart.
Jackson Gerhart mentored Jamie White when White was a youth and Gerhart was living in Silver Spring, Md. White, now chief of the Shippensburg Fire Department, said Gerhart brought a "city mentality and education to Shippensburg. We are a better fire department because of Jackson Gerhart."
Ken Cox, another fellow firefighter, said he was privileged to serve alongside Gerhart for many years.
"Sunday was one of the saddest days of my life," he said. "Sitting outside the ICU was a sobering experience. He laid down his life as he lived it, serving others."
Gerhart was always behind the scenes "working and honoring God and loving his neighbor," the Rev. Dianne B. Salter of First United Methodist Church said.
"I never did a funeral without him calling (beforehand) and saying, 'I'll be there. Whatever you need, I will help.'"
After the service, firefighters stood at attention in the cold rain and saluted as pallbearers lifted Gerhart's casket onto the back of a District of Columbia Engine 17 truck.
Throughout downtown Chambersburg, people stood in the rain and watched the procession. Fire and emergency vehicles, many of them draped in black, lined U.S. 11 to Norland Cemetery. Two ladders made an inverted V over the entrance and an American flag hung from the apex.