It’ll be a show of force to keep a cop killer behind bars.

About 40 relatives of an NYPD officer gunned down in the line of duty plan to flood a parole office in Manhattan today to lobby for the heartless shooter to stay locked up, The Post has learned.

“This man should remain incarcerated for the rest of his life!” said Noreen Keegan-Connelly, 42, the niece of Police Officer Joseph Keegan.

“There is no forgiving evil. He should not be let out — ever.”

On June 19, 1980, Keegan, 41, spotted Bruce Lorick, 22, trying to evade paying a fare in the 59th Street/Columbus Circle subway station. Keegan tried to eject him, but Lorick grabbed the cop’s gun and shot him in the head before fleeing into Central Park.

Lorick, now at Sing Sing, was sentenced to 25 years to life and will appear before a parole board during the week of Feb. 21 for his fourth such bid for freedom.