MONTREAL -- A 41-year-old man who was the subject of an Amber Alert involving his six-year-old boy was charged on Monday in the slaying of the child's mother.

The single charge of second-degree murder was filed at the courthouse in Saint-Jerome, Que. It is unclear, however, when the suspect will appear in court as he is hospitalized in Ontario after an alleged suicide attempt.

Police issued an Amber Alert on Thursday after the boy's mother was found dead inside a home in Saint-Eustache, Que., north of Montreal.

The child and his father were stopped by police in eastern Ontario nearly 24 hours later.

A spokesperson with Quebec's provincial police said a prisoner transfer will take place when the suspect's health permits.

Pierre Gauthier, the suspect's lawyer, said his client was in a coma and doesn't know if he regained consciousness.

Meanwhile, authorities in Quebec are continuing their search for a missing 71-year-old man whose vehicle was used in connection with the child's disappearance.

There has been no word from Yvon Lacasse since his car was stolen late Thursday at a rest area in Lachute, Que.

Police found the boy in Lacasse's stolen vehicle on Friday and arrested the child's father.

Officers on Monday looked for the missing man with the use of a helicopter.

They searched a 500-kilometre stretch of highway between Mont-Tremblant and Rouyn-Noranda.

"Co-ordinating searches along a highway with citizens is dangerous, so we're using the chopper and some specially trained members of the force," said Quebec provincial police Lt. Martine Asselin.

Asselin said police are asking citizens in all the areas the suspect visited while on the lam to keep an eye out for Lacasse.

An intensive search with volunteers over the weekend in Lacasse's hometown of Lachute, about 80 kilometres northwest of Montreal, turned up no signs of the 71-year-old.

Lacasse is described as bald with brown eyes, five feet, five inches tall, and weighs roughly 100 pounds.

Quebec police said they are also looking for a bearded male witness in his 40s apparently seen with the suspect on Thursday night in Rouyn-Noranda.

An Ontario couple who witnessed the arrest of the father in the Amber Alert case said the details are still vivid.

The suspect was caught by police in their backyard.

Barb Friske of Dacre, southwest of Renfrew, Ont., said she was washing dishes when she heard a sound.

"It sounded like someone coming into our yard with a flat tire," she said Monday.

A vehicle went through a ditch and came to a stop at a rock fence on their property.

She and her husband were about to help the occupants when they heard a police helicopter overhead followed by a heavily armed officer yelling at them to get inside the house.

Ontario police were eventually able to subdue the suspect.

Friske said she knew about the Amber Alert, but had last heard the man was spotted nearly 90 minutes away in Napanee, Ont.

"When we saw the young lad and the father come out of the backyard, that's when everything clicked," Friske said.

Friske said she saw the young boy only briefly. He was crying and she offered him a frozen treat to calm him.

The Ontario provincial police said the boy was handed over to Quebec youth protection.

-- With files from Stephanie Marin in Montreal.