Behnam was born on May 20, 1963, in the city of Damavand. He continued his studies in the same city and received his diploma in Mathematics from the Sokhan High School.
At the age of 18, he was employed at the Ta'avon-e Sanfi Credit Fund located on Shahid Motahari Street - Takht-e Tavoos. Ultimately, one year later, on May 4, 1982, a number of members of the MKO terrorist group entered the place and, through deceit, introduced themselves as Committee forces, claiming they were looking to arrest counter-revolutionary elements. Suddenly, they opened fire with a barrage of bullets, assassinating and martyring 5 employees of this credit fund, including martyrs Behnam Shahmohammadi, Ebrahim Bazrafshan, Alireza Rahimisefat, Heydar Riahi, and Ahmadreza Kolachahi Sabet.