Armed police officers were called to Cardinham Woods after a man was seen waving around a 15 inch machete.
Darren Lewis made the 999 call yesterday afternoon after he came across the man while walking his dog.
"We were walking down the path and when we came out of the woods we saw this chap with a great big machete," Mr Lewis said.
"The blade was around 15 inches long.
"He was swinging it around – not at anybody just waving it about and swinging at the grass"
Mr Lewis, who lives in St Austell, said he was immediately concerned for the safety of children and families in the area.
"With it being a family place and lots of kids being around it was really worrying so I called the police.
"He was making no attempt to hide it and just kept swinging it around.
"It was an accident waiting to happen," the 33-year-old added.
Within minutes an armed response unit, four patrol cars and a police dog were on the scene and the suspect, who is thought to be in his sixties, was detained.
"He didn't seem like he was with it at all," Mr Lewis said.
"He just didn't seem quite right. It was very unnerving."
Families, walkers and cyclists who were at the woods out in the sunshine were asked to evacuate the area while the police detained the suspect.
The area was fully reopened a short time afterwards.
