An object, thought to be a bottle which was partly filled with a flammable liquid, was allegedly thrown into a property in Chapel Close, Wick on Wednesday, May 25, according to Sussex Police.
Police said a witness saw a man throw the alight object into the victim’s back garden ‘and ran away with his arms on fire’.
Officers are now appealing for information following the ‘suspected arson’.
A spokesperson added: “The fire is thought to have started between 11pm and 11.30pm and was extinguished by crew from West Sussex Fire & Rescue who determined the fire had been started deliberately.
"The fence, part of the shed, a bike and garden equipment were set alight causing around £700 worth of damage.”
Crime Investigator Stefanie Peffer said the fire ‘could have been fatal’.
She added: “Due to the quick action of brave members of the public, the fire caused limited damage however it could have been fatal or it could have caused devastating damage.
"We are currently treating this incident as arson with intent and we urge people with information which could help officers with their investigation to come forward.”
Anyone with information or who has video footage from around the time of the incident, which could help officers with their investigation, is asked to report it to police online or call 101 quoting serial number 1455 of 25/05.Alternatively you can report this information to Crimestoppers anonymously by calling 0800 555111.