DAVID Nicol put his hand through the living room window when he saw his former girlfriend and one of his friends in her house.
Blackburn magistrates heard that Nicol accused his former partner of "rubbing his face in it" before putting his hand through the glass.
Nicol, 23, of Broadgate, Darwen, pleaded guilty to criminal damage
He was given a conditional discharge for six months and ordered to pay £30 compensation and £20 costs.
David Macro, prosecuting, said Susan Healey was sitting in the living room of her home with a friend just after midnight.
Her relationship with Nicol had finished four weeks earlier.
He was shouting abuse and said he was going to kill them both before pushing his hand through the window.
Miss Healey noticed there was blood on the broken glass and called for the police.
Asked if he had anything to say, Nicol, who was not represented, said: "That was my friend in there, not hers, that's why I was angry."
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