A forensic investigative services truck sits parked outside an Ajax home on Wednesday afternoon.
A 29-year-old man will appear in court this morning on multiple charges in connection with the deaths of a mother and two of her children in Ajax.
The suspect, who is identified in court records as Cory Fenn, will appear in court in Oshawa.
The man is now charged with three counts of second-degree murder in connection with the deaths of the woman, her son and her daughter. He was initially charged with attempted murder in connection with the daughter's critical injuries, but she died Wednesday evening in hospital.
The mother and her son were found dead in an Ajax home late Wednesday morning.
Police have not yet identified the victims, but said the mother is 39 and the son is 15.
Police were called to the home on Hilling Drive, near Lake Driveway West and Westney Road South, at 11 a.m. Wednesday, when officers located the bodies of the mother and son.
The call came after a friend of the mother went to check on her and was met by a man at the door who refused to let her in, before he left in a vehicle.
The 13-year-old was also at the home and was rushed to hospital in life-threatening condition before dying of her injuries on Wednesday night.
A third sibling, a girl who was not at home at the time of the incident, was found safe, Tudos said.
Durham police's tactical support unit arrested the man in Oshawa after a search. Tudos said he believes the suspect had a relationship with the mother, but is not the father of the children.
Police said they are investigating the deaths as a domestic incident and said they were not the result of a 'random attack.'
Officers located an unoccupied vehicle in the area of Brock Road and Highway 401 that is believed to be connected to the suspect.