A man in his 60's was shot dead near Ballyhaunis last night.
Gardai say the fatal shooting occured in Aghamore just before midnight.
A man in his 60's was pronounced dead at the scene, which is being preserved for technical examination.
A man in his 80's has been arrested in relation to the incident and is being detained at Castlebar Garda Station under Section 4 of the Criminal Justice Act.
Gardai are appealing for anyone with information to contact Claremorris Garda Station at 094 - 9372080 or the Garda Confidential line 1800 666 111