Hello and welcome. Thank you for your query. It is not possible to reach a diagnosis for a deceased person as the person himself/herself is not available to answer our queries, which is why we conduct an autopsy (investigation post-mortem i.e. after death) to find the cause of death. But, from the description you have given us, it does look like your friend had some cardiovascular event. There could thus be many possibilities. In my opinion there could be a chance of a: Myocardial infarction (heart attack), leading to an arrest, some other ischemic event Pulmonary embolism (a possible circulating clot that lead to obstruction of a major vessel in the lung) HOCM (hypertrophic obstructive cardiomyopathy)- usually seen in young individuals And so on... Also important is the history of the person. You could wait for a report from the doctor who would have examined her either at the scene or once she was shifted to a hospital for confirmation of death. My sincere condolences for your loss. I hope I have succeeded in answering your questions, you could write back to us anytime for further clarifications. Best wishes.