Grief-stricken Canadians are dropping off flowers and stuffed animals outside a Quebec daycare center that was smashed into by a city bus, killing two children and sending six to the hospital

LAVAL, Quebec — Parents returned Thursday to the Montreal-area daycare center where two children were killed when a bus rammed into the building, stopping to grieve and to recount the difficult moments they witnessed.

André Beaudoin, a father of a 2-year-old boy who attends the center in Laval, said he had to push through debris Wednesday to help pull injured children from under the bus, which had shattered the front of the building.

“I managed to get four out; the last girl … her head was stuck really bad,” he said.

Beaudoin said he had just parked to drop off his son when he saw the city bus barrel into the daycare. He said he ran into the building, and although most of the children had fled, “we heard the screams” of those still trapped.

Two children, both 4years old, were killed and six were hospitalized. Pierre Ny St-Amand, a 51-year-old driver with the Laval transit corporation, was arrested at the scene and later charged with two counts of first-degree murder as well as seven other charges, including attempted murder and aggravated assault.

Large sheets of plywood covered the damaged wall Thursday, next to a cheerful sign with pink letters bearing the name of the center, Garderie Éducative Ste-Rose. Piles of debris from the damaged roof and interior lay in the snow.

People, many in tears, stopped by to pay their respects and add to the growing memorial of flowers and stuffed toys in a snowbank outside the center where two 4-year-olds died in the incident.

Two of the six children had been released from the hospital, while four youngsters remained under treatment, Montreal health officials said.

Montreal’s Sainte-Justine children’s hospital said in a statement that the two children remaining there were in a “favorable” state of health. Two kids remained at a Laval hospital, and doctors said their lives were not in danger.

Pierre Ny St-Amand, a 51-year-old driver with the Laval transit corporation, was arrested at the scene Wednesday. He faces two counts of first-degree murder as well as seven other charges, including attempted murder and aggravated assault.

Authorities said Thursday that they were still trying to understand what could have led someone to drive a bus into the daycare center.

“The motive remains incomprehensible still today,” Public Security Minister François Bonnardel told reporters in Quebec City.

Asked what authorities could have done to prevent the incident, Bonnardel said: “No one can predict this kind of event. No one can predict that someone gets up in the morning, takes off with a bus and decides to hit a daycare with a bus.”

Witnesses said the driver was delirious after exiting the bus, tore off his clothes and screamed as several people restrained him on the ground until police arrived.

Late Wednesday, a police cruiser and two officers were stationed outside St-Amand’s home on a quiet suburban street about 10 kilometers (six miles) from the daycare center. Several neighbors described him as a quiet, pleasant father of two young girls.

One man, Thanh-Ry Tran, said his family got together with St-Amand’s family a few times a year, adding that their wives would sometimes help each other in picking up or dropping off children. He said St-Amand had never shown signs of distress.

Lionel Carmant, the government minister responsible for social services, told reporters in Quebec City that regional health officials in Laval found no evidence that St-Armand had received care for mental health issues.