According to the charge-sheet of the case, on 22 February, 2013, a demonstration of around 3,000 members of 12 parties including Jamaat-e-Islam, BNP and Hefazat took place in Khulna demanding abolition of International Crimes Tribunal, release of arrested war criminals and chanting anti-government slogans.

Headed towards the Ganajagaran Mancha in the city, the procession at one point faced police obstruction. Later, the people from the procession allegedly open gun fires towards police and blasted cocktails.

In self-defence police also fired 20 rounds of bullets in the air. During the clash some members of police got injured by the blast. Later, police arrested 26 people from the spot.

Later in the day, sub-Inspector of Sonadanga police station, Alamgir Kabir filed a case against 26 people including Mamunul Haque.

According to the charge-sheet of the case, Mamunul Haque ordered his followers to vandalise the demonstration of Ganajagaran Mancha and attack police during a waz mahfil (religious sermon) held at Moylapota mosque a day before the incident.

The charge sheet was submitted on 21 April, 2015 by investigation officer of the case sub-inspector Md Moktar Hossain against some 107 people.

On 3 September, Mamunul was transferred to Khulna district jail from Kashimpur high security central jail in Gazipur.

Earlier on 5 June, a Narayanganj court sent Mamunul to Kashimpur central jail on completion of his 18-day remand in six separate cases.

Mamunul was arrested from Jamia Rahmania Arabia Madrasah in Mohammadpur by a joint team of Tejgaon Division police and DMP's Detective Branch on 18 April.

He was remanded for 18 days till 5 June, in six different cases filed on the allegations of rape and vandalism. Among the cases, three were filed by the district police, two by the CID, and one by the Police Bureau of Investigation (PBI). The former Hefazat leader currently has 27 cases against his name.