Three of the five convicted killers were hanged on Thursday midnight.
According to the case detail, followers of Purbo Bangla Communist Party leader Nuruzzaman Laltu opened fire on the rally at around 5:30pm on Feb 16, 1999.
Laltu, sentenced to life in the case, was gunned down later.
JaSaD organised the rally on the premises of a school some 30 kilometres west from Kushtia district headquarters to protest against terrorism.
Aref, then a central leader of the then ruling Awami League’s partner JaSaD, was the chief guest.
Witnesses said Aref stood up for his speech after five others spoke at the rally.
The group of assassins, armed with firearms, surrounded the dais when he began his speech saying, “We will have to be united to launch a social movement against terrorism, extortion.”
Khorshed Alam, then a leader of Bangladesh Chhatra League, was moderating the programme.
He said the assailants were 12 to 15 in number.
“Seven to eight of them walked up to the dais. They were members of Laltu Bahini,” he said.
Case documents say the leader of the assailants, who had tied red towels around their heads, asked the speakers and audience not to move.
They shot Arhia Union Parishad member Ajibor Rahman when he tried to run away.
They then fired into the air and asked for the names of those on the dais, the witnesses told the court.
Shamser Mandal of Talbarhia village was shot dead at once when he wanted to leave.
Then the killers shot and killed JaSaD leaders Lokman Hossain, Yakub Ali, and Israil Hossain.
Aref was still on stage.
“Please don’t kill my men this way. What is our fault? We will leave politics if you ask us to do so. What will you gain from killing us?” he asked them.
The leader of the assassins asked his name.
Hearing Aref’s name, he said they had in fact been looking for him.
Two others then shot and killed Aref.
The weapons used in the attack included an SMG, rifles, pistols and many other firearms.
According to the case details, assailant Mannan Molla was waiting near the scene with a walky-talky and a heavy gun in his hands during the attack.