You know... If he wasn't such a genuine, gentle, and loving person towards her, he would be one of the toxic lovers out there good at manipulating people with words. Hehehe.
I think someone push his mother to fall from bridge or using some medicine to make her fall by herself.
I wonder if his mother can make clinic in her name (not sure if clinic she make it or her son make it for her) why she let her son go to stay with her husband father?