A father has been jailed for at least 26 years for killing a man who asked if his crying daughter was all right.
Matthew Quesada, 26, over-reacted when 63-year-old Alan Smith approached the child, and took it as criticism of his parenting, the Old Bailey was told.
He went home and then stabbed kindly Mr Smith five times in a "frenzied and silent" attack after tracing him to a local cafe.
Quesada, of Leyton, east London, was found guilty of murder and sentenced to life.
Judge Peter Rook told him: "You are a very dangerous young man. This was a truly grave crime. Your reaction was wholly unexpected and out of proportion. You over-reacted and took this as a slight on your parenting."
Quesada's partner Maria Brigitte, 26, was found guilty of assisting an offender and given a nine-month jail sentence suspended for two years and 200 hours unpaid work.
The court heard Mr Smith was stabbed in front of his partner and daughter in revenge for asking if everything was all right with the little girl.
Mr Smith was in the BB Cafe in Leyton, east London, on March 26 last year when he asked Quesada about the crying child.
Quesada replied: "What's it to do with you? Go away."
Mr Smith was "eager to avoid confrontation", and so went with his partner, daughter and son-in-law to the nearby Roma Cafe. Meanwhile, Quesada took his daughter home to his partner Brigitte, and came back with a knife that he used to wordlessly attack Mr Smith.