Complex sentence: That happened because Niharika's brother (Shaam) was an undercover cop and when goons found out they killed the whole family, the only one who survived was Niharika, but she had a bullet in her head.
Split into simpler sentences: That happened because Niharika's brother was an undercover cop and when goons found out they killed the whole family. The only one who survived was Niharika but she had a bullet in her head.