Two children are dead and one man is in custody after what police described as a "family drama" in Laval's southwest end Monday evening.

Laval police received a 911 call around 6 p.m. and found the two children — an 11-year-old boy and a 13-year-old girl — inside a home on Lauzon Street in Laval's Ste-Dorothée sector, on the island north of Montreal. 

laval police operation

The two children were rushed to hospital in critical condition where their deaths were later confirmed. 

Hours after the horrific discovery, Laval Mayor Stéphane Boyer offered his condolences to the family in a post on Twitter, in which he wrote "all of Laval is in mourning."

He added Laval police officers are being mobilized to shed light "on this untold sadness."

A 45-year-old man was also hospitalized in critical condition and is now in police custody in hospital. Police did not disclose the relationship between the man and the two kids.

He is expected to meet with investigators Tuesday and is scheduled to appear in court later that same day. The charges to be laid against are yet to be determined.

"We wish to give our dearest sympathies to the families for their loss," said Const. Erika Landry, a spokesperson for Laval police, during an update for the media at the scene Monday evening. 

The children's mother was taken to hospital to be treated for shock, Noovo Info reported. 

A resident who lives on Lauzon Street told CTV News he saw a heavy police presence on his street Monday evening. He also said he saw paramedics trying to resuscitate a patient inside an ambulance before the vehicle left the scene.

"The police response was quite rapid," the man said.

laval police operation

Quebec Liberal Party Leader Dominique Anglade also offered her condolences to the victims' family on Monday, writing on Twitter that she was "wishing all the strength in the world to the family and loved ones of this tragedy."

With files from CTV Montreal's Kelly Greig