It happened at the 600 block of West Ridgecreek Drive around 1 a.m.
Police said once he entered the home, the ex-boyfriend got into an argument with the woman of the home and her new boyfriend.
The ex-boyfriend was shot and killed inside the home.
Officers interviewed family members and patrons of the party to find out what exactly happened.
Police said it looks like a case of a home invasion and self-defense.
The woman's ex-boyfriend did have a weapon, police said. Investigators weren't yet certain if he used it because there were multiple shell casings in the house and weren't sure which weapon they came from.