West Bengal minister Subrata Mukherjee died after suffering a cardiac arrest on Thursday evening, The Indian Express reported. He was 75.

The Trinamool Congress leader had been admitted to a hospital in Kolkata a week ago for heart-related complications. He had undergone procedures to clear blockages in his heart and was scheduled to be discharged on Friday.

But Mukherjee suffered a cardiac arrest on Thursday evening and the doctors could not revive him, West Bengal Chief Minister Mamata Banerjee said.

“I have seen many disasters in my life but the passing away of Subrata Mukherjee is the biggest disaster in my life,” Banerjee said at the hospital. “A person of his stature, who loved the party and people of his constituency, will not come again.”

Mukherjee was the West Bengal chief minister’s political mentor. She described his death as a personal loss, according to PTI. “I still can’t believe he is no longer with us,” Banerjee said. “He was such a dedicated party leader.”

West Bengal minister Firhad Hakim said Mukherjee’s death was an irreparable loss. “This void will never be filled,” Hakim said, according to The Indian Express. “He was an inspiration to all of us. We have no words to describe this loss.”

Mukherjee had joined that Trinamool Congress in 2010, PTI reported. He was with the Congress before that.

After the Trinamool Congress’ victory in the 2011 West Bengal Assembly elections, Mukherjee was made the public health engineering minister, The Indian Express reported. He also got the additional charge of the rural development ministry.

In May this year, Mukherjee was arrested in the Narada bribery case along with minister Hakim, Trinamool Congress MLA Madan Mitra and former party leader Sovan Chatterjee. They were granted bail by the Calcutta High Court.

The case involves videos published by Narada News, in which several Trinamool Congress leaders were allegedly seen accepting cash in return for favours. The videos, shot by the website’s Chief Executive Mathew Samuel, were released ahead of the state Assembly elections in 2016.