The man was arrested on suspicion of murder after a woman and fiveyear- the old woman was found stabbed death in north London.
It is assumed that the victims mother as well as daughter and were known to the arrestee, the Metropolitan Police said.
The officers were called to home in Brookside South, Barnet, today at 13:37. There were paramedics and air ambulances. also deployed.
They are found woman, 37 years old, and a girl with stab wounds and they were pronounced dead on the stage.
Human, also 37 years old, was arrested and the Metropolitan Crime Squad is investigating.
Chief Superintendent Sara Leach described it as “an incredibly complex scene”. for in first defendants.
“Specialist detectives are working to establish that took place and a man in care,” she said.
“Although they are open minded about what happened place I would like to reassure the residents in local area that at this stage there is nothing to indicate that anyone was still involved in this incident.
“I would call anyone who saw or heard something unusual earlier today, or in the last days to come forward and talk to the police. Your information may be vital, as the investigation moves forward.”
Information can be obtained by calling 101 with reference 3590/21JUN.
Alternatively, people can contact Crimestoppers anonymously on 0800 555 111.

