A man has died in hospital after he stopped breathing during a citizen's arrest outside the Hyde Park Hotel in North Perth.

It is alleged the 36-year-old man was breaking into cars when he was chased by a group of men.

The ABC understands they caught him at the rear of the hotel, but during a struggle the man went into convulsions.

Police said he was not breathing when they arrived at the scene but was revived and taken to Royal Perth Hospital where he later died.

Detectives from Major Crime and forensic officers spent several hours at the scene last night gathering evidence.

Investigations are continuing and no charges have been laid.

Local barber Denny Huang said he saw what he believes was the same man earlier in the night.

He said the man was carrying a very large hammer and was smashing cars and also the water pipe at the front of his shop.

"He was crazy, he would smash anything, would smash anything, anyone in his way," Mr Huang said.

"The way he holds his weapon, he was threatening pretty much everybody. That's how I feel really.

"You don't walk around with a hammer... not in the city, not a hammer that size."

It is the second incident involving a citizen's arrest in the past four weeks.

Late last month, a man died in the Perth suburb of Lockridge after he was pinned to the ground by a man who suspected him of breaking into his home.

The man, believed to be a former police officer, was walking his dog at night when he returned to find two men acting suspiciously outside his home.

One man fled but he managed to catch the other and was restraining him when he died.