Police hunting a racist firebomber have warned shopkeepers to plan an escape route should they come under attack.
Police are linking three attacks
Khizar Hayat, 40, died and three others were injured when Pricecutter, near the Oval in south London, was targeted, trapping staff inside.
Detectives think the same attacker was responsible for two other blazes at Asian-owned businesses.
Shop owners have been urged to make sure staff know the quickest way to get out of their premises in an emergency.
"They must ensure at all times that the means of escape are available, unblocked and people can get through them," he said.
Police are linking the suspect with fires at a Tulse Hill newsagent on 14 April and a South Norwood corner shop on 20 April.
Det Supt Heselden said: "It's my opinion that we're dealing with a serial firebomber who is targeting small Asian businesses.
"We must catch him before he commits another arson attack in which someone else may be killed."
The suspect is described as a black man, barrel-chested with a shaved head, aged 30 to 35, about 5ft 10in tall with a strong jaw line and rough skin.
A second man, who was trapped along with Mr Hayat, is critically ill in hospital.
Two others who ran through the flames suffered minor burns.