A snake expert said it was possible that the python was spooked and simply clung to whatever it landed on. Police are treating the deaths in Campbellton, New Brunswick, as a criminal investigation.
Autopsies on Noah Barthe, 4 and his brother Connor Barthe, 6, were being performed Tuesday.
The brothers had been visiting the apartment of a friend whose father owned an exotic pet store on the floor below, Royal Canadian Mounted Police Sgt. Alain Tremblay said at a news conference in Campbellton. Tremblay said the African rock python was being kept inside the second floor apartment, not inside the pet store as authorities had previously stated.
Steve Benteau, a spokesman for the provincial Natural Resources Department, said no permit was issued for an African rock python and the province wasn't aware it was being kept at the apartment. The department said the snake is generally only permitted in accredited zoos, unless there is a special permit.
Tremblay said the snake was housed in a large glass enclosure that reached the ceiling of the apartment and escaped through a small hole in the ceiling connected to the ventilation system. He said the snake made its way through the ventilation system and moved toward the living room, where the boys were sleeping. The pipe collapsed and the snake fell.
The friend of the boys was sleeping in another room and was unharmed.
The pet store owner, Jean-Claude Savoie, told the Global News television station that he didn't hear a sound and discovered the "horrific scene" when he went into his living room on Monday morning.
"I can't believe this is real," Savoie said.
He said the boys were the children of his best friend and were often at his apartment to visit his son. Savoie said the python, which he has had for at least 10 years, had been kept alone in its enclosure and was not handled by anyone else.
Police said the snake was killed by veterinarian. It was sent for a necropsy to confirm the type of snake and help understand what may have caused it to attack.
Family spokesman Dave Rose, the boys' great-uncle, said the brothers had spent Monday at Savoie's family farm and played with different animals before staying over at the apartment. Rose thanked the community for their support and asked for privacy.
The snake was about 4.3 meters (14 feet) long, Tremblay said. He said police were looking at whether the store followed the province's regulations on exotic animals.
"It's a criminal investigation," Tremblay said. "We're going to look at all avenues."
The RCMP's Major Crime Unit is continuing the investigation, with the assistance of a reptile expert from the Magnetic Hill Zoo in Moncton, New Brunswick.
"I guess we can assume that given the size of the snake that certain things occurred, but the pathologist will be identifying the cause of death," Tremblay said.
Tremblay said police spoke to the store owner briefly and will meet with him again.
The town's deputy mayor, Ian Comeau, said the Reptile Ocean shop was licensed to operate and "everything was according to our bylaws, to the provincial guidelines." He said he saw alligators, crocodiles and snakes when he toured the shop with the fire department about two years ago.
Snake expert John Kendrick, a manager at the Reptile Store in Hamilton, Ontario, said it sounds like the python was not enclosed properly and might have been spooked. He called the strangling deaths "very unusual" but said African rock pythons tend to be a little more high-strung.
"It's very odd that one would go out and seek out a person. They don't recognize us as food," he said.
Pythons can sense heat, and if they are startled they can grab something, Kendrick said. He said snakes are very long and their muscles run lengthwise through their body, so they are not very stable unless they are holding on to something.
"A snake that size that was just trying to hold on securely enough to make sure he felt like he wasn't falling or going anywhere; he has enough muscle power to cut off circulation," he said.
It's possible that the python was just holding on to what it landed on, Kendrick said.
"Once they are in constricting mode, any part of their body that is touching something that moves, they'll wrap it," he said. "I've seen snakes with two different prey items at the same time, one with the back of the body and one with the front. It could have been an incident like that."