Bangladesh Unravels 3-Year Mystery of Machete Killers 2 militant Islamist groups are behind the attacks, authorities say By Evann Gastaldo, Newser Staff Posted Jun 9, 2016 5:35 PM CDT 16 comments Comments Bangladeshi security officers inspect the site where blogger and author Ananta Bijoy Das was killed in Sylhet, Bangladesh, in 2015. (AP Photo/A.H.Arif) (Newser) – Since 2013 in Bangladesh, at least 39 activists, bloggers, foreigners, and religious minorities have been fatally struck down by mysterious machete-wielding figures on motorbikes. Now, authorities say they finally know who is behind the attacks, the New York Times reports. The chief of the police counterterrorism unit says that an investigation discovered that two militant Islamic groups recruited and trained volunteers to carry out the killings, and that authorities think they've identified the leaders of both groups and are working on bringing them in. Things started coming together for authorities after a 23-year-old was found to be carrying a machete and a pistol and was arrested recently. Six days later, two 19-year-old men were arrested while fleeing the site of one of the fatal attacks, and they said the 23-year-old was also involved in the attacks. From there, other revelations followed. Authorities say the goal of the terrorist groups was to convert Bangladesh from a mix of religions to a strictly Islamist culture. The Times has an extensive look at the three years of terror.