Scott Hain used his own gun to fire several shots into his 30-year-old wife, Meleanie, while her video chat was active and perhaps as she washed dishes in their kitchen, police said. Scott Hain, 33, later killed himself in an upstairs bedroom.
Meleanie Hain's loaded pistol - with a bullet ready in the chamber - was in a backpack hanging from the front door.
The couple's three young children were home just before the murder-suicide, but authorities stopped short of saying they were home at the time.
The online friend heard a scream and turned to see Scott Hain firing, they said.
He "observed Scott Hain standing over where Meleanie was and discharging a handgun several times," Lebanon Police Chief Daniel Wright said at a news conference.
The man, who was described as a friend of both Scott and Meleanie Hains, called emergency police dispatchers.
Meleanie Hain became a voice of the gun-rights movement last year when she fought for the right to carry a holstered pistol at her young daughter's football games. Other parents complained, prompting a sheriff to revoke her concealed-weapons permit, a decision a judge later overturned.
"I'm just a soccer mom who has always openly carried (a firearm), and I've never had a problem before," Hain said last fall. "I don't understand why this is happening to me."
The Hains later sued the sheriff who had revoked her open-weapons permit. The $US1 million ($NZ1.37 million) suit, which claims they suffered emotional distress and lost customers for her home baby-sitting service, remains pending against Lebanon County Sheriff Michael DeLeo.
Scott Hain, a parole officer, owned the 9mm handgun used to kill his wife. He then killed himself with a shotgun. Police found several handguns, a shotgun, two rifles and several hundred rounds of ammunition in their Lebanon home.
Friends and neighbors told police the couple had been having marital problems. However, Scott Hain was living at the home at the time, Wright said.
Their three children are ages 2, 6 and 10.
Neighbor Aileen Fortna has said the children told another neighbor that "daddy shot mommy."
