The son of a pizzeria owner used Facebook to track down the man who terrified his mum and beat up a customer, a court heard.
Elizabeth Collins was left traumatised after the violent incident at her takeaway premises in Woodlands, Doncaster - so her son decided to turn detective to find her attacker.
He trawled the social networking site to identify the local man who had lashed out in violence while waiting for his order.
Prosecutor Richard Sheldon told Doncaster Crown Court: “It was her son who did his own detective work on Facebook which led to the arrest of Charnock.”
His efforts landed Reece Andrew Charnock in the dock and the judge locked him up for 14 months.
Charnock, aged 20, of Recreation Road, Woodlands, pleaded guilty to inflicting grievous bodily harm on Mark Lewin and using threatening behaviour towards Mrs Collins, who is in her 60s.
Trouble started at Isabella’s pizzeria on Great North Road when he became abusive towards one of the employees, who is Iranian, said Mr Sheldon.
He was also arguing with someone and swearing via his mobile phone and, when Mrs Collins asked him to behave, he threw his phone on the floor so was asked to leave.
The owner moved to eject him from the shop but Charnock shouted at her: “What are you going to do, you bitch?”
When he grabbed her shoulders and began struggling, Mrs Collins became scared and started crying so two other customers intervened, one of whom, Mr Lewin, persuaded him to leave.
But a few moments later, when Mr Lewis popped his head out of the door, the defendant was still there and punched the left hand side of his jaw.
Mr Lewin was taken to hospital where he needed an operation to plate and screw his fractured lower jaw back together, said Mr Sheldon.
Mrs Collins had seen Charnock land the blow to Mr Lewin’s jaw.
Charnock had previous convictions for assault and affray.
Heidi Cotton, defending, said Charnock had made significant alterations to his lifestyle over the past year since he had become the father of a baby daughter.
“He has a troubling record for offences of this nature committed when in drink, but since May last year he has ceased to associate with the group of individuals he was socialising with,” she said.
“He has curbed his drinking and activities which clearly landed him in trouble.”
Judge Jacqueline Davies, sentencing Charnock to 11 months in a young offenders’ institution for the GBH and three months consecutively for the threatening behaviour, told him: “Your behaviour towards this lady was entirely inappropriate.
“The court has to impose a sentence of immediate custody. It was a serious matter, you showed repeated violence and you have a record. You caused a serious injury to someone who suffered a lot of pain and had to undergo surgery.”