Complex sentence: It is revealed that Peeta has been "hijacked"-brainwashed using Tracker Jacker venom-to kill Katniss, and he tries to choke her to death upon their reunion.
Split into simpler sentences: It is revealed that Peeta has been'hijacked', brainwashed using Tracker Jacker venom, to kill Katniss. He tries to choke her to death upon their reunion.