A man accused of fatally stabbing and bludgeoning six people in Tennessee and Alabama was targeting his wife and killed the others first so they couldn't stop him, authorities said Tuesday.

Jacob Shaffer, 30, is charged with six counts of homicide. He bought two stun guns Friday, the day before the victims were found, indicating the attacks were planned, District Attorney Charles Crawford said at news conference.

Lincoln County Sheriff Murray Blackwelder said officers found out about the crimes after Shaffer called 911. He was still at the scene when officers arrived and found five people dead in two neighboring rural homes. A sixth man was killed at a business about 30 miles away in Huntsville, Ala.

Investigators believe 38-year-old Traci Shaffer was the last person to die and that the couple had been having marital difficulties, Tennessee Bureau of Investigation spokeswoman Kristin Helm said. Shaffer "went out of his way" to kill Traci's father, Billy Hall, 57, and brother Chris Hall, 34, in their home across the street from hers in Lincoln County.

"In this case, he wanted to make sure the father and the brother who were in close proximity wouldn't interfere with him killing his main target," Helm said.

Helm said investigators think Shaffer then went to Traci Shaffer's duplex and killed his stepson, Devin Brooks, and a neighbor, Robert Berber, both 16, before killing his wife.

The only person left unharmed inside the home was Jacob and Traci Shaffer's 4-year-old daughter, Helm said.

"She was probably asleep," Helm said. "As far as what she witnessed, I don't know."

Helm said investigators are still trying to figure out the motive in the beating death of the first victim, 50-year-old Sidney Wade Dempsey, who was found at Huntsville's Hall Cultured Marble Granite in Huntsville, Ala., where he worked and was allowed to live. Unlike the stabbings in Tennessee, Hall died of blunt-force trauma, police said. A family friend said the business belongs to Traci Hall's family.

"I think the guy (Dempsey) was just in the wrong place at the wrong time. I think the guy (Shaffer) just decided to start there," said Huntsville police Sgt. Mark Roberts.

Helm said Shaffer made a statement to police, but would not say if he confessed to the murders.

"It's a pretty solid case for us," Helm said. "We've got everything we need to prosecute him."