A Buddhist monk remains in an induced coma while a temple caretaker is recovering after a nail gun attack between the pair on Sydney’s southwest outskirts.

Police believe one man shot the other in the head with the nailgun and then shot himself on Wednesday afternoon but authorities don’t know who was holding the weapon.

The men, aged 29 and 59, were each shot once in the head at the Vat Ketanak Khmer Kampuchea Krom temple in Rossmore.

• Two critical after nailgun attack

Police said the pair were the only two in the cottage being constructed on the property when the nail gun was fired.

“It’s an unusual event,” Green Valley Superintendent James Johnson told AAP.

“We still have not been able to work out the full circumstances of what happened.

“It’s very early days and we’re having difficulty with the language barrier.

It has been reported monk Karuna Kim, 29, remains in an induced coma with a 10cm nail in his head at Liverpool hospital on Thursday.

Temple caretaker Tha Lam’s condition has improved and remains stable.

Police investigations are continuing.

Mr Lam claims he was the victim in the bizarre incident.

Friend Vannara Kim translated Mr Lam’s version of events as he lay in a hospital bed on Thursday.

Mr Lam claimed Mr Kim shot himself before turning on him.

“He suddenly heard snap of the nail gun and he was aware the monk shoot himself,” Vannara Kim told the Seven Network.

“After that, he (Mr Kim) grab him and shoot him.”