Irish Rail staff were forced to tackle a man as he smashed 16 windows on a Dart service with two emergency hammers.
The 32-year-old was arrested by gardai on suspicion of criminal damage, which happened on a stationary Dart in Bray station at 4.30pm yesterday afternoon.
No other passengers were onboard the carriage, which was extensively damaged.
As a result, capacity was reduced on some morning rush-hour services today between Howth/Greystones and Malahide/Bray due to the vandalism.
Irish Rail said a man took the emergency hammers from a carriage and proceeded to break 16 windows form the inside.
"The driver and station staff became aware of the situation and only their quick thinking prevented more damage being caused," a spokeswoman said. "They were first at the scene and tried to stop him from breaking more windows.
"They managed to detain him until gardai arrived," she added.
A garda spokesman said the suspect was later released without charge.
A file is being prepared for the Director of Public Prosecutions.