Quick thinking by three workmates returning from a roofing job in Acacia helped collar a suspected arsonist.
Irishman Barry O'Hare and his Rockingham Roofing workmates CJ Webber and Conor Breslin spotted two bushfires, one burning intensely, along Morrison Road in Midvale about 6.30pm on Thursday.
Suddenly a shirtless man sprinted across the road in front of them.
"We knew straight away," Mr O'Hare said. "Once we'd seen him we thought he definitely had something to do with it."
Mr O'Hare, 25, instructed his mate to park their utility before the trio, helped by others, cornered the alleged offender in a nearby field.
He said the man was "fidgety and nervous" so he offered him a cigarette while they waited for police.
Police have charged a 25-year-old Midvale man with wilfully lighting fire likely to injure. It will be alleged he lit six fires that night.
The workmates' boss Tim Black said he was proud of his three employees.