blood pressure bottomed out

what could cause bloodpressure to bottom out, have hysterics, coma, and death with in 4 hours? this happened to my mother. she had diabetes, high blood pressure, and had had a quadruple bypass 5 years earlier. my sis ter had committe suicide 1 week before, and her doctor said she died of a broken heart! that is the only answer i have been given. was told they didn't know what had happened. Help! i really need an answer.