(CNN) The mayor of the Polish city of Gdansk, a well-known critic of his country's right-wing government, died on Monday, one day after he was stabbed by a man who rushed on stage during an open-air charity event.

Thousands of people witnessed Sunday's attack on Pawel Adamowicz, 53, who was rushed to hospital where he underwent a five-hour long operation before succumbing to his injuries. He was stabbed in the heart and stomach.

The stage where Pawel Adamowicz was stabbed in Gdansk.

The brazen attack took place during the finale of a children's hospital charity event, known as the Great Orchestra of Christmas, when Adamowicz was thanking everyone who had helped raise funds for medical equipment.

The 27-year-old suspect, who was arrested, is a Gdansk resident with convictions for bank robbery and had spent time in prison. Gdansk city press officer Dariusz Wołodźko said the suspect came onstage shouting, and blamed the mayor and his party for his conviction and imprisonment.

Born and raised in Gdansk, Adamowicz had long been a fixture of public life in the city. He entered local politics in 1990 as a local councilor before serving as Gdansk's mayor, a position he held for more than 20 years.

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