Hi Charlotte, I think you have suffered a Fracture Penis! Sudden gush of blood from penis may result from fractured penis or if you have a coagulopathy- a disorder of blood not getting clotted and a local erosion. Fractured penis is a surgical emergency- it occurs when there is a vigorous buffeting going on and there is a missed move and erect hard penis hits the perineal structures and it s soft tissues get torn, large swelling occurs instantly and Penis may get a bend deformity. Some times an injury in meatal area or penis skin may lead to small rent and can lead to noticeable bleed in those patients who have clotting disorders like low platelets, high INR, on medications etc. Immediate action is to prevent the bleeding and hematoma formation by direct manual pressure. Then to report in an Emergency Room as soon as possible. Wish you a great health.