The man later exchanged gunfire with authorities and died of a gunshot wound after hitting several deputies and a state trooper, Cumberland County Sheriff Earl "Moose" Butler said.
"He just went wild," Butler said of the shooter. "I mean, shooting at random. He just turned it loose, that automatic. He unloaded it every time I think he pulled up there" in front of the victims' house.
The violence began before 7 a.m., when 41-year-old Valerie Michaelis called 911 for help, authorities said. Michaelis and her husband, Andrew, were arguing and she said he was holding her at gunpoint.
Investigators said Valerie Michaelis got the gun from her husband, who then pursued her with a knife. She fled to her father's house.
Seven people were in the house when authorities say Andrew Michaelis drove by in his truck and discharged a 30-round magazine from what authorities described as an assault rifle. He killed two people: his wife's father, 61-year-old Gary Simpson, and Simpson's 10-year-old grandson, Trekwan Covington. Among those in the house was Ryan Michaelis, 13, who was there "because of problems in the home," Butler said.
His father knew Ryan was in the Simpson home, the sheriff said.
Michaelis drove away and then returned a second and third time to fire into the house and from inside the truck, Butler said. Deputies arrived in between the volleys, and one who entered the home was hit in the chest, back and shoulder.
"Later on we heard a series of bang, bang, bang, bang, bang, bang," said Luz Ross, who lives beside the Simpson home. "It was like war over that side. And a little later on there were a series of high-powered bang, bang, bang, bang, over that area."
Other deputies pursued Andrew Michaelis through a wooded area into an adjoining neighborhood and onto a residential street. He continued firing at deputies, who returned fire, Butler said.
Michaelis died at the scene, but it wasn't clear if the deputies killed him or if he took his own life. Authorities found another 50 to 60 rounds in his truck "so this man was prepared to take some lives this morning," Butler said.
One neighbor who lives near the woods where the suspect was killed, Jacarria Bethea, said she didn't get up when she heard shots because she's used to hearing gunshots at nights. Another neighbor, Cheryl Feeley, attributed those nighttime gunshots to people firing guns into the air in the woods, not at each other.
Neighbors have had disagreements but never fired weapons, she said. "It's a scare for everybody in the neighborhood," Feeley said.
The house where the shooting occurred is on a corner lot in a neighborhood of mostly mobile homes on foundations. Its front door had what appeared to be gunshots, and tiny pieces of shattered, green glass were in the street. Spatters of blood stained the front porch, which was covered with broken glass from a shattered storm door. A tiny American flag sticker sat among the glass.
The deputy shot while in the house was in stable condition, Butler said. A second suffered a grazing wound to his head while a third suffered minor bruising when a bullet struck her duty belt, which prevented the bullet from entering her body.
Another deputy escaped injury when a bullet penetrated his uniform but didn't strike his body. A state Highway Patrol trooper suffered a shrapnel wound when a bullet went through his vehicle.
Associated Press National Writer Allen G. Breed contributed to this report.