Complex sentence: Eddie is shunned by Melissa who was using him as a means to make Nick jealous and he goes downstairs, after Melissa leaves the house, Eddie is killed when Jason rams a knife into his neck.
Split into simpler sentences: Eddie is shunned by Melissa who was using him as a means to make Nick jealous and he goes downstairs. After Melissa leaves the house, Eddie is killed when Jason rams a knife into his neck.