The police have opened an investigation paper on a government pensioner holding the honorific 'Datuk' title, for allegedly opening fire last Thursday, on another pensioner who was mistaken for a monkey.

City police chief ACP Sum Chang Keong said the investigation paper was opened under Section 39 of the Firearms Act 1960.

"The pensioner who has a licence for the gun has handed over the firearm to the police to facilitate investigations," he told reporters after an assembly session at the Pasir Puteh police station here today.

In the incident which occurred about 1.40pm, another pensioner was plucking fruits from a rambutan tree when he was shot in the arm by the 64-year-old Datuk.

Earlier, the Datuk was relaxing at his brother-in-law's house in Kampung Chepor when he noticed some movement in the tree located about 50m away.

Thinking a monkey was foraging for rambutans, he fired a shot in the direction of the tree, only to hear a man groaning.

The Datuk sent the injured man to the Raja Permaisuri Bainun Hospital where the victim was reported to be in stable condition.