The extent of injuries from explosive forces decreases exponentially with distance from detonation. Injuries at close range result in characteristic injuries with amputation, body dissection, and massive tissue defects [11]. In the present case, there were severe soft tissue injuries as a sign of direct injury to the body by material of the explosive device, so it can be assumed that the explosive device was close by and detonated in the area of the head. The additional injuries inside the cranial cavity and the skull (fractures, contusion hemorrhages) speak for the massive impact of violence. In the case of blast injuries, different types of injuries can be distinguished depending on the point of origin. In addition to primary injuries caused by the detonation wave at the interface of air and tissue, there may be secondary projectile injuries caused by fragments added to the explosive device or by projectiles from the surroundings. The ballistic effect of the projectiles depends on the mass, velocity, and shape of the fragments and can therefore range from very small penetrations to large lacerations. Often the fragments are smaller and irregular in shape, so there is a strong deceleration into air and tissue despite high initial velocity. The penetration depth and the extent of injury of the projectile wounds are therefore often limited. In the present case, the projectile injuries were also caused by fragments from the ball bomb [12].

The roundish skin perforations were morphologically similar to gunshot wounds with a central non-adaptable substance defect and an epidermis-free marginal zone (abrasion ring). Most of the skin lacerations had a black rim. Considering the effective charge of projectile bombs, which generally consists of metal salts and mainly black powder, it is not surprising that the skin changes can hardly be distinguished from an injury caused by a usual projectile. The injury pattern would be comparable to a bullet penetration caused by a close range shot, whereby the projectiles usually get stuck on the opposite side of the body beneath the skin or harder resistances like bones. In the present case, the fragment was small and more irregularly shaped than usual projectiles; the dispersal of the effect charge therefore only led to a small penetration depth of the tissue. Besides the effect charge, a piece of cardboard discolored with soot was found in the skin laceration. This was most likely the outer shell of the bullet bomb, which is usually made of cardboard. Hot explosive gases and resulting secondary fires can also cause thermal injuries such as the burn to the young man’s upper arm [13, 14].

Why the accident occurred could not be clarified by the police investigation. From the investigation documents, it could only be inferred that the fireworks, which had been used that evening, had previously been purchased through a “seller via WhatsApp” due to the sales ban. On the basis of the injury pattern of the roundish skin defects (Fig. 8a), the impression of a bent posture arises, in which the hands may have been supported on the thighs, which could have brought the respective localizations “closer together” and protected the abdomen so to speak (Fig. 8b).

Schematic illustration of the injury pattern of the round skin lacerations (A). Possible body posture at the time of the explosion (B)

Such a posture could have been adopted, for example, when igniting the explosive device, while the ball bomb ignited too quickly and immediately, for example. Also, which is more likely, a renewed “look down the tube” because the firework did not ignite immediately would be conceivable. The detected blood alcohol concentration would support this tragic behavior.