After a concert on Tuesday, renowned Bollywood singer Krishnakumar Kunnath, known professionally as KK, died of a suspected heart attack.

The famed 53-year-old singer sang at a concert in Nazrul Mancha, Kolkata, just hours prior to his death on May 31.

According to the Times of India and other local media, Kunnath became ill while singing at a concert in Kolkata. He reportedly complained of feeling extremely cold after the show and wished to return to his hotel.

A video leaked hours after singer KK’s sudden death following a concert in Kolkata, depicting him appearing unwell as he was carried out of the venue. He returned to his hotel, where his condition was said to have worsened. He had chest trouble and died on the way to the hospital, according to reports.

The singer’s death has yet to be determined, but a post-mortem report is due soon. According to local sources, a case of unnatural death has been filed with the police.

KK, who was born in Delhi in 1968, started his career performing advertising jingles and went on to perform in many Indian languages, including Tamil, Telugu, and Kannada, before landing his big break in film music.

He leaves behind a wife, a son, and a daughter.

As soon as news of his death came, tributes to the late artist flooded social media, including one from India’s Prime Minister Narendra Modi.

“We will always remember him through his songs. Condolences to his family and fans.” Indian Prime Minister Narendra Modi wrote on his twitter handle.

Over the course of his nearly three-decade career, KK sung over 500 Hindi songs and over 200 songs in other Indian languages. He had also won plenty of awards, including two Screen Awards for Best Male Playback Singer.