The association targeted Lt Col NS Simpson, the Inspector General of Prisons, who was infamous for his mistreatment of the prisoners in the jails. The revolutionaries decided not only to murder him, but also to strike terror in British colonial circles by launching an attack on the Secretariat Building - the
Writers' Building in the
Dalhousie Square in
Kolkata. On 8 December 1930, Dinesh, along with
Benoy Basu and
Badal Gupta, dressed in European costume, entered the Writers' Building and shot dead Simpson. Nearby police started firing at them in response. What ensued was a brief gunfight between the three young revolutionaries and the police. Some other officers, like Twynam, Prentice, and Nelson, suffered injuries during the shooting. Soon, police overpowered them. However, the three did not wish to be arrested.
Badal Gupta took Potassium cyanide, while Benoy and Dinesh shot themselves with their own revolvers. Benoy was taken to the hospital, where he died on 13 December 1930. ==The trial and hanging==