Two men facing death row for the 2015 machete murder of American-Bangladeshi writer and anti-extremist blogger Avijit Roy have escaped prison in a brazen plot.

Mainul Islam Shamim and Abu Siddique Sohel were snatched away by suspected extremists on motorbikes who sprayed chemicals in one police constable’s eyes and punched another in the face while they were being taken to court in Dhaka, Bangladesh, on Sunday. The chaotic scene apparently distracted the police officers guarding the convicts, who were among a dozen men facing charges at Dhaka Anti-Terrorism special tribunal.

The entire country has been put on red alert because authorities fear the men may seek revenge. “A massive manhunt has been launched to capture them and their helpers,”Asaduzzaman Khan, the home minister, said, according to Reuters. A $20,000 reward has been offered for information about their whereabouts.

Roy was allegedly hacked to death by a group of machete-wielding Islamic extremists outside Dhaka University book fair in 2015 after his work was widely published. His wife Rafida Bonya Ahmed survived the attack but lost a thumb before she narrowly escaped. The U.S. government offered a $5 million reward for anyone with information about the group that killed Roy.

He was one of more than a dozen bloggers who criticized religious conservatism in the Islamic world who suffered a similar fate. The killers were among a group of 13 members of the banned extremist group Ansar Ullah Bangla Team militant group, which was inspired by al Qaeda.

The group tweeted justification of their act, “These two atheist-apostates have published books that have attacked the honor of the Prophet (Mohammed) and mocked Islam,” they wrote at the time.

Mainul and Sohel were also convicted with six others and sentenced to death for killing publisher Faisal Arefin Dipan, who published much of Roy’s controversial writings.