Officers are examining CCTV footage after a shop manager was stabbed to death during a suspected robbery in an east London shopping centre.
Jamie Simpson had worked in the store for three years
Jamie Simpson, the assistant manager of the Matalan store at Kingsland Shopping Centre in Hackney, was attacked as he was cashing up at 2000 GMT on Saturday.
Officers believe three attackers "lay in wait" before confronting Mr Simpson.
The attackers are believed to have run from the store via the rear car park in Dalston Lane.
Officers remain at the scene and the area has been cordoned off.
Det Insp Lawrence Smith said: "We believe that the three individuals involved lay in wait at the store and then confronted the assistant manager.
"The description that we have of them is of three young black males. We do have CCTV which is being looked at today."
The officer added there were no witnesses to the murder.
Mr Simpson, who had worked at the store for the past three years, was found by staff shortly after the attack in an office area where he was working.
Earlier Det Insp Jackie Sebire said: "Mr Simpson was known as a reliable and diligent member of staff."
"Mr Simpson was completing his day's work when he was fatally assaulted during a suspected robbery at his store."
Police believe the store was targeted and extra police officers have been deployed to the area.
Officers have appealed for information on anyone in the shopping centre who was seen "acting suspiciously" in the evening or witnessed the assailants fleeing the scene through the car park.