Gardaí arrested a man in Collinstown last night after having to chase him down.
They had been following the man in his 30s by car at around 10pm last night, before the man ditched the car and ran out on foot.
He was eventually caught in a park in the west Dublin area.
Gardaí discovered and seized a gun and ammunition and also seized the man's car. He is currently being detained under the Offences Against The State Act.
The gun is undergoing a ballistic and forensic examination by the Garda Technical Bureau.