A Denham Springs woman told Livingston Parish Sheriff's investigators she feared for her life, when she shot and killed a 70-year-old man who walked onto her front porch--tripping a burglar alarm. It happened late Wednesday night. 70-year-old Joe Cash Jr. was a cancer patient. He was staying at a home about a block away.  His illness made him frequently disoriented and  it's believed he wandered onto the wrong porch. Deputies says it's unlikely charges will be filed against Mamie Moffat of Denham Springs, but the incident is still under investigation.