A young man was left with burns and may have lost the sight in one eye after youths threw a firecracker under his friend's car overnight.
Peter Bywaters, 24, was helping fit a set of spotlights to his friend's ute about 6.30pm on Verna Street, Gosnells, when five youths drove up in a blue Astra hatchback displaying P plates.
One of the occupants lobbed the home-made explosive under the utility. Mr Bywaters picked it up without realising what it was.
It exploded seconds after he dropped it, burning his arm, bursting his eardrum and leaving him with a shard of debris lodged in his eye.
"Half the street came out because they thought I'd been shot," he said.
He condemned the youths' actions and whoever had sold them the fire cracked.
"What were they thinking, what if there had been a child standing on the other side of the ute?" he said.
The car was driven by a young blonde woman, with another woman in the front seat and three men in the back.
A couple of hours later in the neighbouring suburb of Kenwick, a blaze started by firecrackers came within metres of homes.
About 40 volunteer firefighters battled to bring the fire under control as it licked at backyard fences.
The fire was reported just before 9.30pm and was thought to have been started by people playing with firecrackers, Peel district fire officer Rick Darlow said.
About 5ha were burned before the blaze was brought under control.
Police are investigating both incidents.
Anyone with any information should contact the police on 131444.