Bigger kills Mary in Native Son

Bigger is carzy! how could he possibly do that to Mary , Bigger feared Mrs.Dalton for finfding out that he was there in Mary's room and his only way out was to shut her, to kill her without no pitty killed her. but what will happend to Bigger? How would they know what happend to Mary? after all Bigger did not want to kill her but he had to do something before she talked.