Saifuddin Mollah (24), the SFI leader, had gone to a meeting of Suryakanta Mishra, leader of the opposition in West Bengal assembly, at Baruipur town.
When he returned to Sitakunda under Baruipur police station, where he lived, some people abducted him, the sources said.
Later, he was beaten up and was found in a critically injured condition at Kajirabad under the same police station.
After he was taken to hospital, the doctors declared him brought dead, the sources said.
Sitakunda panchayat was earlier held by the Trinamool but it was now being run by the CPI(M).