The man was at one fire at a property on Short Street in Portland, in western Victoria, when he collapsed at 8.30am.
The three fires were reportedly lit between 7am and 7.30am on Camira Street, Short Street and within a bin on the corner of Percy and Gawler Streets, according to police.
No one was injured in the fires, which are being treated as suspicious.
The Country Fire Authority confirmed the death of the man this morning, which was not believed to be caused by the fire.
The volunteer, who is yet to be identified, collapsed at the scene.
Emergency services on scene administered CPR but he sadly died.
“Our deepest sympathies go out to the member’s family, friends and colleagues at the Portland brigade,” a statement from the CFA read.
“Our wellbeing team is providing support to all involved at this sad time.”
It’s believed the man may have suffered a medical episode and his death is not being treated as suspicious.
WorkSafe will investigate and detectives from the Arson and Explosives Squad will also attend the scene.
Anyone with information is urged to contact police.