A Camborne man sparked an armed response call-out to Constantine on Wednesday evening after harming himself with a knife.
The police and an ambulance were called to a house in Brillwater Road, round the corner from the village's primary school, at 4.25pm.
A 33-year-old man "was in a fairly agitated state and was in a possession of a knife," a Devon and Cornwall Police spokesperson said.
He was reported to have "harmed himself already" and a firearms unit were called in due to the risk posed by an unstable man wielding a deadly weapon.
There was talk of drafting in a police negotiator, but after a two hour stand-off the man appeared at the front door of his house and appeared "calm and compliant," the spokesperson said.
He was detained under Section 136 of the Mental Health Act and taken into protective custody at Camborne Police Station.
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