Paweł Adamowicz, mayor of the Polish city of Gdańsk, has died after being stabbed in the chest on stage at a charity concert on Sunday night.

The 53-year-old, who had held this position since 1998, suffered more than five hours of operation overnight. "We could not win," Polish Minister of Health Łukasz Szumowski said Monday afternoon.

Dr. Tomasz Stefaniak, director of the Gdańsk Hospital where Adamowicz was treated, said: "With deepest regret, we must inform that, unfortunately, we lost the struggle for the life of the president of the city . Honor to his memory. He died just now. Prosecutors will investigate the cause of his death. "

The alleged perpetrator, a 27-year-old man from Gdańsk who committed violent crimes, was released from prison last month, revealed Monday. After the assault, the assailant told the crowd that he blamed Adamowicz's former Civic Platform for being jailed in 2014 for a series of violent attacks.

Adamowicz, a popular and liberal mayor, has long been considered a hate figure in far-right circles for his vigorous defense of migrants and refugees and LGBT rights, but nothing indicates that the attack was motivated by political considerations.

Some in Poland Blame the attack on a more general rise in social tensions and a growing prevalence of hate speech. Even before his death, silent demonstrations were scheduled for Monday in a number of cities.

The assassination of Adamowicz, a mayor of six warrants who often interfered freely with the citizens of his city, shocked Poland. In Gdańsk, the city's flag has been lowered and a mass is planned for later in the day.

Politicians from all walks of life have condemned this aggression, including Prime Minister Mateusz Morawiecki, Interior Minister Joachim Brudziński and other members of the ruling Nationalist Party, the Justice and Law Party. (SIP). Adamowicz was known as an opponent of PiS.

"I am very sorry for the tragic death due to the criminal attack of Mayor Paweł Adamowicz. We express our solidarity with his family, "said Jarosław Kaczyński, leader of the PiS, in a tweet from a party spokesman.

Donald Tusk, president of the European Council and former leader of the civic platform, said: "Paweł Adamowicz, mayor of Gdańsk, a man of solidarity and freedom, European, my good friend, was murdered. That he rests in peace. "

Polish President Andrzej Duda will meet with party leaders on Monday to organize a march against violence and hatred.

Adamowicz was part of the democratic opposition formed in Gdańsk under the leadership of Lech Wałęsa in the 1980s. After leaving Civic Platform, he was re-elected for a sixth term as an independent candidate last fall.

As mayor, he was a progressive voice, supporting sex education in schools, LGBT rights and tolerance of minorities. He showed solidarity with the Jewish community when the windows of the Gdańsk Synagogue were broken last year, strongly denouncing vandalism.

It is understood that Adamowicz's wife, Magdalena, was in the United Kingdom at the time of the attack. The Polish government sent a plane to London to bring it back to Poland.

Good Non Profit contributed to this report