A 30-year-old man has been arrested on suspicion of assault after the death of his 73-year-old father.
The man was arrested after police were called to a report of a domestic incident in Laneshaw Close, Darwen at about 7.10pm.
The father was taken to Blackburn Royal Infirmary but was pronounced dead at 8.20pm.
Inspector Graham Ashcroft, of Blackburn Police, said: "A 30-year-old man has been arrested at the address on suspicion of an assault. An investigation is continuing. It is a domestic incident.
"The man arrested is the deceased's son."
Inspector Ashcroft said the man would be interviewed today
Neighbours in the quiet cul-de-sac said pensioner lived at the address with his wife.
They said the family had moved to the property in recent months.
One said: "They are a lovely couple, a really nice couple."
Another said: "It is a complete shock" close."
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