Three people were killed and several others were injured as Zakaria group opened fire on the villagers of Khulna's Moshiali. One was also beaten to death by a mob.
The angry villagers staged a protest on Friday in the area demanding the execution of four brothers – Jakaria, Kabir, Jafrin and Milton.
Upon receiving the news, additional police forces were deployed in the area to avoid further turmoil.
Police arrested Jahangir, Jakaria's assistance, over his involvement in the murders and illegal possession of bullets.
Previously at 9pm on Thursday, Jakaria group shot Nazrul Islam, 60, and Golam Rosul, 30, dead.
Eight-ten others including Saiful Islam sustained gunshot wounds at that time.
Jakaria, Jafrin, Kabir and Milton handed over a blameless man named Mujibur with local weapons to police around 5:30pm on that day, the locals said.
They went to Jakaria's house to find out about Mujibur's arrest.
At one the stage, the locals got into a brawl with the group. And armed Jakaria, Jafrin, Kabir, and Milton suddenly opened fire at them.
Later, the injured were taken to Fultola Upazila Health Complex where Nazrul and Rosul succumbed to bullet injuries.
The other injured were shifted to Khulna Medical College Hospital after initial treatment. Among them, Saiful, 22, died at 12:15am.
As the news broke out, the angry villagers beat Jakaria's aide and cousin Zihad Sheikh, 30, to death at around 2am.
Later, the furious villagers also vandalised and set fire to 10 houses, including the houses and business establishments of Awami League leaders Jakaria, Jafrin, Kabir and Milton.
Earlier, Jakaria became a candidate for the post of secretary in the election of Moshiali Purbapara Mosque committee and yesterday was the day of the election.
However, the villagers turned into Jakaria's opponents as the Awami League leader is involved in drug peddling, illegal arms trade and loan-sharking, the locals said.
Jakaria was removed from the post of assistant publicity secretary of Khanjahan Ali Thana Awami League on Thursday night for allegedly shooting a few villagers dead, Awami League's Khan Jahan Ali Thana unit President Sheikh Abid Hossain said.
Also, the locals on Friday marched demanding the execution of Zakaria, Jafrin, Kabir, and Milton when the law enforcers came to the spot.
Police tried to calm them down promising to arrest the culprits quickly and bring them to justice.
Khan Jahan Ali police station Officer-in-Charge Md Shafiqul Islam said, "The situation is under control now. Bodies of all the victims were taken to Khulna Medical College Hospital morgue."
Kanai Lal Sarkar, additional deputy commissioner of Khulna Metropolitan Police said, "Four people have been killed so far. Police teams are conducting drives to detain the perpetrators involved in the clash and shooting. However, no case was filed over the incident up to 6pm on Friday."