A Stranger Pressed my moms Boobs. What can i do?

10 years ago me and my mom travel in a rush train. there was a huge crowd in the compartments. we stand for whole journey of 2 hrs in the train. in the crowd at stations many people coming in and out to compartments where train stops at various stations. due to crowd peoples body touches others people. a man standing next to my mom very close to her from backwards when passengers come to our compartment he lost control and fell over my mom. when he fell, he pressed my moms one boob. he ask sorry to my mom and my mom react nothing. after some minutes that man again fell over my mom and this time he pressed my moms boob tightly and hold it for some seconds. my mom do nothing. i fell surprise on seeing this why mom do not react for that? after some minute that man voluntarily squeezed my moms boobs and my mom kept silent. what is the meaning for that? iam confused please anyone help me