Investigators found prescription anabolic steroids in the house and want to know whether the muscle man was unhinged by the drugs, which can cause paranoia, depression and explosive outbursts known as "roid rage."
Benoit's employer, the WWE, instituted a new and supposedly tougher drug policy just last year after the death of another wrestler was linked to steroid use, reports CBS News national correspondent Byron Pitts.
Authorities offered no motive for the killings, which were spread out over a weekend, and would not discuss Benoit's motive or state of mind. No suicide note was found.
"I'm baffled about why anybody would kill a 7-year-old," District Attorney Scott Ballard said. "I don't think we'll ever be able wrap our head around that."
Benoit, a Montreal native whose nickname was "The Canadian Crippler," was known for his wholesome family man image. His wife, Nancy, was a wrestling stage manager who worked under the name "Woman." They met and fell in love when their wrestling story lines intertwined.
When he won the world heavyweight championship, Benoit (pronounced ben-WAH) hoisted the belt over his head and invited his wife and child into the ring to celebrate.
Nevertheless, Nancy Benoit filed for a divorce in 2003, saying the couple's three-year marriage was irrevocably broken and alleging "cruel treatment."
She later dropped the complaint, as well as a request for a restraining order in which she charged that the 5-foot-10, 220-pound Benoit had threatened her and had broken furniture in their home.
In the divorce filing, she said Benoit made more than $500,000 a year as a professional wrestler and asked for permanent custody of Daniel and child support. In his response, Benoit sought joint custody.
The bodies were found Monday afternoon in three rooms of the house, off a gravel road.
Benoit's wife, 43, was killed Friday in an upstairs family room, her feet and wrists were bound and there was blood under her head, indicating a possible struggle, Ballard said.
The son, Daniel, was probably killed late Saturday or early Sunday, the body found in his bed, Ballard said.
Benoit, 40, apparently killed himself several hours and as long as a day later, Ballard said. His body was found in a downstairs weight room, his body found hanging from the pulley of a piece of exercise equipment.
The prosecutor said he found it "bizarre" that the WWE wrestling star spread out the killings over a weekend and appeared to remain in the house for up to a day with the bodies.
Toxicology test results may not be available for weeks or even months, he said. As for whether steroids played a role in the crime, he said: "We don't know yet. That's one of the things we'll be looking at."
Neighbors said the Benoits led a low-key lifestyle.
"We would see Chris walking in his yard from time to time. He wasn't rude, but he wasn't really outwardly warm," said Alaina Jones, who lives across the street.
Jimmy Baswell, who was Benoit's driver for more than five years, placed a white wreath at the Benoits' gate. "They always seemed like they were the happiest people," he said.
World Wrestling Entertainment said on its Web site that it asked authorities to check on Benoit and his family after being alerted by friends who received "several curious text messages sent by Benoit early Sunday morning."
The WWE, based in Stamford, Conn., said authorities asked that it not release further information on the deaths.
"WWE extends its sincerest thoughts and prayers to the Benoit family's relatives and loved ones in this time of tragedy," the company said in a statement on its Web site.
"He was like a family member to me, and everyone in my family is taking it real hard," said fellow Canadian Bret Hart, a five-time champion with the World Wrestling Federation. The federation has since changed its name to World Wrestling Entertainment.
Benoit had maintained a home in Atlanta from the time he wrestled for the defunct World Championship Wrestling. The Fayette County Tax Assessors Office lists the value of the house, on more than 8.5 acres, at nearly $900,000.
The WWE canceled its live "Monday Night RAW" card in Corpus Christi, Texas, and USA Network aired a three-hour tribute to Benoit in place of the scheduled wrestling telecast.
Benoit had two other children from a prior relationship.