A man is facing charges after stripping down to his underwear at a Bunnings Warehouse before going on a bizarre rampage with a chainsaw.

Police say the man had been inside Bunnings in Cannington but when he got to the front counter he tipped his items onto the ground and began taking his clothes off before returning to his car in his underpants.

He allegedly on the wrong side of the road before crashing into a fence inside a car park about 5.45pm yesterday.

Camera Icon The man’s mother says she is desperate to get help for her son.

Bystanders filmed as the man smashed the rear window of his car with a golf club before throwing out a baby seat and starting up a chainsaw.

Witness Feraidun Hakimi said the man's behaviour was frightening.

"The Bunnings staff they were pretty terrified, the girls that came out, they were shocked and they were like white as a ghost or something," Mr Hakimi said.

"When he managed to turn the chainsaw on, everyone just took a step back.

"It was pretty like scary, it was just crazy. It was weird, unusual behaviour, you don't see it every day."

Camera Icon The man was taken to hospital after being arrested by police. Credit: Feraidun Hakimi / 7 News

The man continued to rant until police arrived a short time later.

He completed a forward roll when officers ordered him to get on the ground and was arrested.

The 27-year-old was taken to hospital and is tonight facing drug and traffic charges.