Jasenovac concentration camp
On the night of August 29, 1942, the camp's guards made bets about who could kill the most prisoners.  One of the guards, Petar Brzica, reportedly cut the throats of about 1,360 of the new prisoners, using a butcher knife that became known as srbosjek ("Serb-cutter").  Other guards who admitted taking part in the bet included Ante Zrinušić, who killed about 600 inmates, and Mile Friganović, who gave a detailed and consistent report of what happened.  Friganović admitted to killing 1,100 inmates.  He specifically talked about how he tortured an old man named Vukasin.  He ordered the man to bless the Ustaše leader, Ante Pavelić.  The old man refused, even though Friganović cut off his ears, nose, and tongue every time he refused.  Eventually, he cut out the old man's eyes, tore out his heart, and cut his throat.  Dr. Nikola Nikolić saw this happen.