What did Cato do to Peeta? What dose he threaten to do to Katniss? (. From the hunger games book 1)

He gets free, but when Katniss thinks he's safe, Cato begins strangling him in a headlock. Cato threatens that if Katniss shoots him, Peeta will go over the side too ... Cato, in his body armor, fights the muttations off for an hour before he is dragged into the Cornucopia.