Is being bullied a reason to kill?

I have been interested in the case of the “Molotochniki” since almost a year and a half already. One of the murderers, Nikita Lytkin had a pretty sad backstory. His half-brother shot himself after his mother died, which led to Nikita’s dad falling into a deep depression. He came back to lytkin once in a while but left, and each time he left, he left lytkin more disappointed than before. Apparently lytkin was getting bullied by his peers almost everyday for 8 years, and he once even robbed the house a person that bullied him. His mother stated that he was a very weak person and would let anyone lead him by his hand. Could a reason why Nikita started murdering people be that he wanted to show that he wasn’t weak? (of course murder cannot be excused and there is no reason to take peoples lifes.)