This man was a police corporal in the New York Police Department and also known as Ollie.
A favorite of Captain Mark McCluskey, Ollie worked for Sergeant Joe Galtosino. Ollie was one of McCluskey's first choices in the plot against Vito Corleone at the hospital and made sure no one went near Vito's room until McCluskey called and told him he and Ollie told his younger brother Stanley to leave the hospital unguarded as Tattaglia assassins were sent there to kill Vito.
After the failed attempt to kill Vito Corleone at the hospital Paulie Gatto alerted Joe Galtosino to a party at the Corleone's favorite spot Rosa's. Sergeant Joe Galtosino and Corporal Ollie crashed the party and took Rosa for "questioning" he was listening to Rosa's answers of the questions asked about Aldo Trapani, Marty Malone, Paulie Gatto and Sonny Corleone. He infiltrated rest of party as spy, disguised as a civilian rather. Two years later Ollie, Christopher Ferriera and Stanley are beating a criminal when Aldo shoots Ollie in the back of the head, killing him instantly.