I fear the motive will never really be known. This is a fairly compressive summary -
SQ reveals how the Carpentier family's deaths played out | Montreal Gazette
“Up until he crashed his car with his two daughters in it on the night of July 8, there was nothing to indicate Martin Carpentier posed a danger to his family, police said Wednesday.
He was travelling on the route he was expected to be taking after going out for ice cream, along Highway 20 near St-Apollinaire, close to Quebec City. Forensic investigation of the scene indicates the crash was an accident, that Carpentier lost control of his vehicle and tried to regain it before smashing. A partially eaten ice cream cone was found left behind. Blood traces indicated at least one of the girls had been injured in the accident.
Police contacted the girls’ family to say there had been an accident and the victims were missing. Family members did not say they were worried Carpentier was trying to kidnap his girls, or would harm them, Sûreté du Québec chief inspector Guy Lapointe said. Carpentier was no longer with the girls’ mother, but was reportedly still on friendly terms with her. It was not until the next day that the SQ would issue an Amber Alert, indicating they feared for the safety of the children, Norah and Romy Carpentier, aged 11 and 6.
By that time, police now know, both the girls and the father were already dead.......
.....“For us, up until the moment of the accident, there was nothing that was premeditated or deliberate,” Lapointe said. “It seems the accident was a tipping point because it was as of then that the behaviour, that we can all, I think, qualify as abnormal, came into play.”
Witnesses spotted Carpentier crossing the highway, carrying one child in his arms, the other walking alongside him. It was the last time they were seen alive. Carpentier left behind one of his sandals in the car, and his cellphone. Records show his parents-in-law called him about an hour after the accident.
Within the next 12 hours, Carpentier walked 1.7 kilometres south into the forest with his daughters, breaking into a trailer. He took a shovel and a lighter.
About 750 metres further south “is where the irreparable happened,” Lapointe said. The two girls were killed with a blunt object. Carpentier made it another 2.5 kilometres further south, stealing a ladder from a resident’s property along the way, then took his life. Police would not say how he killed himself.
“What we know now today is that all these events … all occurred in a very small time frame,” Lapointe said. “On the morning of July 9 all the sad events had played out and all three were already dead.”....”
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