An African python that escaped it’s enclosure and killed two young boys has been put down, authorities in Canada say.

4-year old Noah Barthe and his brother, 7-year old Connor, were reportedly on a sleepover at a friend’s apartment over the weekend when they were killed by the giant snake.

Jean-Claude Savoie owns a small pet store–Reptile Ocean–over which he resides in the apartment. He said that the snake must have escaped its enclosure and gotten up into the ceiling ducts somehow, eventually falling down into the living room where the boys were sleeping.

“They were sleeping and they never opened their eyes or nothing. At first, I didn’t even realize. I thought they were sleeping until I seen the hole in the ceiling, everything had fallen and I turned the lights on and I seen this horrific scene,” he said.

The snake, which is believed to be illegal in the area, has been the subject of some mystery. Authorities aren’t sure why it was able to suffocate the boys without biting first, as they usually do.

“It could be that kind of an accident where the snake got in where the kids were and they were just something to hold onto. And then when the kids tried to get away, [it] squeezed tighter,” Professor Neil Ford said. “Even a single adult would have a tough time uncoiling a large snake if it wanted to hold on.”

A spokesman for the Department of Natural Resources, Steven Benteau, says that the species of snake that killed the boys is illegal under the Exotic Wildlife Regulation.

“It is illegal for anyone to keep any exotic species that is not listed in the regulation unless they have a permit from the Department of Natural Resources,” says a statement from the department. “If such an animal is found, it will be confiscated and the person who possesses the animal can be charged under the Fish and Wildlife Act.”

The case is now being investigated as a criminal matter.