38-year-old Gerald Tyrone Murphy was shot during the raid early Sunday morning and died from his injuries.
Murphy is accused of killing 44-year-old Carmenlita Stevens and her 13-year-old son.
Officers initially went to the home on the 200 block of Grand Street on Friday after a relative said they hadn't heard from 44-year-old Stevens in weeks. Authorities soon learned her children hadn't been to school in 12 days.
Police found Murphy in a bedroom. He told them he had her three children, ages 18, 16, and 4, and that he was armed with a gun and explosives. At this point, authorities say Stephens and her 13-year-old son were already dead, likely having been killed two weeks prior.
A standoff with police soon ensued, lasting 37 hours.
Steven's three children, a 4-year-old boy, a 16-year-old girl and an 18-year-old girl, were all barricaded inside with the suspect. Police say Steven's 19-year-old with autism was hiding in the basement and was rescued by officers.
According to police, maintaining the welfare of the children was of the upmost importance. During the days-long standoff, authorities sent meals and bottles of water through a window.
"Our mission over the last 37 hours was to save innocent lives. For days the lives of three innocent individuals was put at risk by the presence of one individual," said Col. Rick Fuentes.
After hours of negotiations, SWAT teams decided to move into the home, setting off a flash bomb.
"We did have evidence there was a deteriorating state of mind. We felt in the next 24 hours he would take action and we needed to interrupt that," said Col. Fuentes.
Murphy sustained a gunshot wound during the takedown after threatening to harm one of the children.
The hostages were safely rescued and taken to area hospitals for treatment and evaluation.
Joseph Bocchini, Mercer County Prosecutor said, "Arrangements are being made for the children to have all medical counseling and all other services that they will need."
Investigators are looking into allegations that the suspect assaulted the teenage girls during the ordeal.
Murphy, a registered sex offender in Pennsylvania, had an arrest warrant out for his failure to register with his new location.
Authorities have not yet released a possible motive and many questions still remain. The victim's family believes he snapped after she tried to kick him out.
Police say they are still trying to sort out all the details and are continuing to investigate.