A video of the lynching went viral on social media
Mehedi Hasan Badal, 40, got involved with Awami Juba League after resigning as Panchlaish BCL president.
Bayezid Police Station Inspector Nurul Absar told bdnews24.com he was shot in front his house at Sher Shah Colony at around 10pm on Tuesday.
He was a follower of Chittagong Mayor AJM Nasir Uddin.
He was declared dead at the Chittagong Medical College and Hospital when he was taken there, SI Zahirul Islam of the CMCH police camp told bdnews24.com.