Ontario Premier Doug Ford and Toronto Mayor John Tory were among those who attended.
Emergency Task Force officers donning grey uniforms and vests also turned out to pay respects.
Investigators have said Northrup was killed in a deliberate act last week while responding to a report of a robbery in a parking lot at Toronto City Hall, and a 31-year-old man has been charged with first-degree murder in his death.
Northrup’s casket will remain in Thornhill until Monday’s funeral at BMO Field in Toronto’s Exhibition Place.
Toronto Police carry Const. Jeffrey Northrup’s casket into the Kane-Jerrett Funeral Home in Thornhill on July 4, 2021. Photo by Ernest Doroszuk /Toronto Sun