David Beston walked into the Trespass outdoor clothing store in Sunderland in February, pointed a knife at a supervisor and warned "open the ******* till or else I'm going to ******* kill you".
Newcastle Crown Court heard as the terrified worker attempted to open the till, Beston helped himself to three jackets, worth £300, then took the £100 he was handed.
As he left, Beston issued a chilling warning that he would come back and kill the victim if he contacted the police.
Prosecutor Jane Foley told the court: "He said 'don't tell the police or I will find out where you live and kill you. I will be back in ten minutes and if I see the police I will kill you'."
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Beston, 22, of Elstree Square, Carley Hill, Sunderland, admitted robbery and having a knife.
He also admitted a second charge of having a knife, which he was carrying when he got arrested the following day.
The brave victim attended the sentence hearing today and read his impact statement to the court.
He said: "This incident has left me feeling terrified and upset.
"I genuinely felt like I was going to die I felt as though the male was going to kill me."
The victim said he had not worked at the store for very long and did not want to go back after what happened.
He added: "No-one has the right to threaten me or steal from the store.
"I felt in shock and extremely distressed."
Mr Recorder Matthew Happold sentenced Beston to three years and five months behind bars.
The judge told him: "The complainant gave his victim impact statement in person and tells me he was terrified.
"He thought he was going to be killed.
"It must have been a horrifying experience for him."
Jonathan Pigford, defending, said Beston is not heavily convicted and had a difficult childhood.
Beston told probation officials he had been on a "drugs binge" the night before and believes he was still under the influence when he carried out the raid.