shahnawaz , 40 , was beaten to death by five thugs because his bike - stuck in traffic - was blocking their way .
his sons , aged nine and 13 , begged bystanders and nearby police for help , but were told to ` call 100 '
victim was rushed to nearby lok nayak jaiprakash hospital but died en route .
a day later , 200 protesters blocked central delhi to demand immediate arrest of the attackers .