A 29-year-old woman with the gestation period of 39-40 weeks was hospitalized into a maternity hospital with vaginal bleeding and sharp abdominal pain that started one hour ago. Objectively, her blood pressure is 180/100 mm Hg. The fetal heart rate cannot be auscultated. Vaginal examination detects hemorrhagic discharge with blood clots. The cervix is smoothed out and fully open. The amniotic sac is intact and constantly tense. The baby is in cephalic presentation, with the large segment directed towards the entrance into the lesser pelvis. The placental tissue cannot be detected. What is the most likely diagnosis in this case?