A mother and her 13-year-old son have died after being stabbed at their home in Stourbridge in the West Midlands.
The woman, in her 50s, who has been named by Sky sources as Tracey Wilkinson, was pronounced dead at the scene.
Her teenage son, named as Pierce Wilkinson, was found in cardiac arrest and was pronounced dead at Birmingham Children's Hospital.
The woman's husband, Peter Wilkinson, remains in hospital in a serious condition with stab wounds to his chest and back after all three were attacked at the property in Greyhound Lane.
Their daughter, Lydia, is away from home at university.
A man in his 20s was arrested in nearby Norton Road after a vehicle was "intercepted" and apparently crashed about 30 minutes after the victims were found.
Superintendent Lee Kendrick said: "What has unfolded here this morning is horrific and heartbreaking.
"Police and ambulance were confronted with an awful scene: a man, woman and boy all with very serious stab injuries."
Detectives said nothing could be done to save the woman and she was pronounced dead at the scene.
West Midlands Ambulance Service said it was called to the property just after 8am and discovered the woman and the teenager inside the house and the husband in the garden.
Two air ambulances were also called out.
The man was arrested after a Land Rover Discovery, stolen from outside the home, crashed nearby.
Police said officers had "intercepted" the car and pictures appear to show it had hit a wall.
The suspect, whom West Midlands Police say was known to them, will be questioned on suspicion of murder and wounding.
"Clearly our investigation is at a very early stage but we understand the suspect was known to the family and may have been living at the address - although he is not a family relative," Superintendent Lee Kendrick said.
"We don't think this was a burglary or a robbery.
"Our investigation is progressing at pace and we are working to understand exactly what the relationship was between the man and the family.
"At this stage we are not looking for anyone else in connection with the incident."
Flowers have been left at the scene. One message read: "RIP Tracey."