Md Ashraf Ali, central assistant secretary of Islami Chhatra Khelafat, gave confessional statement in a case filed over the attack on police on 27 March in Brahmanbaria.
He made the confession under section 164 in the court of Brahmanbaria Judicial Magistrate Rakibul Islam on Friday afternoon.
Md Ashraf, 28, hailing from Astagram of Sadar upazila, is also the vice president of Brahmanbaria Sadar Upazila Islami Chhatra Khelafat.
Muhammad Shahjahan, inspector (investigation) of Brahmanbaria Sadar Model Thana, confirmed The Business Standard about the legal development.
He said activists and supporters of Hefazat-e-Islam attacked police while they were discharging their duty on 27 March in the Nandanpur area of Sadar upazila that left several policemen injured.
On 31 March, Sadar Model Thana's Sub-Inspector Md Sohrab Hossain filed a case in connection with the attack, accusing 21 named and 400/500 more anonymous persons. Shahjahan said that Ashraf was arrested after watching the video footage of the attack.
"Ashraf confessed to his involvement in the attack during the primary interrogation and gave the statement today accordingly.
"He described the whole incident of the attack in his statement," said Shahjahan, adding that so far six people have been arrested in this case.
Men of Hefazat-e-Islam carried out massive violence in Brahmanbaria from the 26th to the 28th of March this year protesting the Bangladesh visit of Indian Prime Minister Narendra Modi.
Some 55 lawsuits have been filed in connection with those incidents, accusing 414 people by names along with over 35,000 unidentified persons.