A mum whose eight-year-old son was stabbed to death by her estranged husband has told how police ignored her fears that he planned to kill him. Photo shows Damira Zinnurova, with her children, undated. His ex-husband, Mustafa Topkaya, allegedly killed their son, Mehmet Topkaya, in Mersin, Turkey. (Damira Zinnurova/Newsflash) Desperate…