The people who died included three adults and three children. All of them were shot to death except for the youngest victim, who was just 10 years old. He died from smoke inhalation, according to the medical examiner's report.
There were a total of eight people in the home. The two survivors were the parents of the alleged gunman, 43-year-old Canh Le. They were also the grandparents of the children who were killed.
Officials said that six sets of remains were recovered from the ashes, and have been identified through dental records and DNA.
WATCH: Officials give update as investigators close deadly East Lansdowne shooting, fire
Officals close investigation into East Lansdowne shooting, fire that left 6 dead
Le, as well as his brother, Xuong, Xuong's wife, Britni McLaughlin-Le, and their children, 17-year-old NaTayla, 11-year-old NaKayla and 10-year-old Xavier, all died inside the house. Officials said the only victim who did not die from gunfire was Xavier, who died from smoke inhalation.
Officials said that they are now closing the investigation, adding that no one will be charged, since the presumed gunman was among those who died inside the home that day.
The incident happened on Feb. 7, when police were called to a home in Delaware County for reports of a child shot.
Investigators said Le got into an argument with his niece, NaKayla.
"Nobody knows what, and nobody knows why. We're never going to be able to answer that question for you," Delaware County District Attorney Jack Stollsteimer said.
Le then went into his room and pulled out a Diamondback DB15 semi-automatic pistol, and proceeded to shoot members of his family, including his brother, sister-in-law and their children.
Le's father made the initial call to police from outside the home, where gunfire could be heard in the background.
Officers quickly responded in an effort to rescue the injured child and were met with gunfire upon arrival.
After shooting his family members, Stollsteimer said Le went to the third floor of the house, where he began shooting at the officers.
"The police response was absolutely heroic. In fact, it was textbook. Some of the things that happened that day from our law enforcement officers should be taught in our police academy," Stollsteimer said.
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East Lansdowne police Officer John Meehan, 44, and Lansdowne police Officer David Schiazza, 54, were shot during the incident.
CHOPPER VIDEO: Officers shot while responding to shooting involving child
Chopper video from the scene showed one officer being dragged away from the area after being injured.
Meehan and Schiazza have since been treated and released. Both officers have more than two decades with their respective departments.
They are both said to be recovering well.
Stollsteimer said about 15 minutes after officers arrived, Le set the home on fire before taking his own life.
The house quickly went up in flames as first responders stood back for safety reasons.
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Investigators were not able to determine how the fire was set or what, if any, accelerants were used.
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Stollsteimer said Le's remains were found near a gun that was also recovered from the fire remnants. It was the only weapon found at the scene and bullets removed from the officers' vehicle matched that gun.
WATCH | Chopper video: Officers dragged to safety after being shot in Delaware County
"That weapon, that Diamondback DB15 semi-automatic pistol, was the weapon that was used to kill the other members of his family, except for young Xavier, and then he used it to take his own life after risking a catastrophe for the entire community by setting the house on fire," Stollsteimer said.
Court records show that Le was arrested in 2006 in Delaware County and charged with making terroristic threats, trespassing and disorderly conduct. Details of the incident were not immediately available, but the first charge was later dropped, and he was put in a diversion program on the two lesser charges, leading him to serve 32 hours of community service and pay $1,400 in fines during a year of probation.