Passengers of the 155 bus were forced to get off the bus and find another route home after the door of the bus was smashed.
Two young men were seen running away from the scene, former TD Noel Rock who was on the bus told Dublin Live.
Many on the bus were weighed down with Christmas shopping as they shuffled off the bus looking for another way home.
It is unclear what was thrown but it hit the bus while it was moving along the Botanic Road in Glasnevin.
Noel Rock said he saw "two young males" running away from the bus when it happened.
He said: "Two young males were seen running from the bus. Not entirely sure what was thrown but it was while the bus was moving so it could've hit anywhere/anyone."
The popular former representative said the incident made life a "bit tougher" for decent people just going about their lives.
He said: "The bus can’t go anywhere, so all passengers have to get off or switch to another bus. Families coming back from town with Christmas shopping. Just makes life that bit tougher on decent people going about their lives.
"Life is hard enough for people worrying about Covid."
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