Someone at my high school impaled himself with one. He tried to stop a run away discus with the javelin and he tripped. Miraculously it missed all of his vital organs.
Same thing happened at the Air Force Academy in the 70-71 time frame, as I recall. Someone was running across the athletic fields and didn't notice the javelin sticking into the ground in front of him. Jammed the end straight into his chest... We were quite a ways away but saw the ambulance come out.