"In the absence of any other possible motive, I'm working on the basis that these are racially-motivated attacks," said Detective Superintendent Dick Heselden, of London's Metropolitan Police.
"We must catch him before he commits another arson attack in which someone else may be killed.
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Heselden was speaking as he released more details into the death of Khizar Hayat, who died Thursday when a lighted missile was thrown through his Price Cutter shop, on Clapham Road, in the Kennington district of south London.
Hayat, who is of Kashmiri origin, was trapped in the building as the fire took hold and was declared dead at the scene by firefighters.
Another man is still critically ill in hospital.
"We are now linking two other arson attacks that have occurred in south London this month," Heselden told reporters.
The first happened at a newsagent in nearby Tulse Hill, Brixton, on April 14 when a customer was burnt on both legs after a petrol bomb was thrown into the shop.
The second