Fatal attack? Depends on where victim is stung
All stingrays use the same attack mechanism regardless of size - a sting, up to 20cm long in a bull ray, located near the base of the tail.
The sting contains a sharp spine with serrated edges, or barbs. A venom gland sits at the base of the spine and a membrane-like sheath covers the entire sting mechanism.
When a stingray attacks, it needs to face its victim. Then it flips its long tail upward over its body and strikes whatever is in front of it.
In most cases, when the sting enters a person's body, the pressure causes the protective sheath to tear. The sharp, serrated edges of the spine then sink into the victim's flesh, and venom flows into the wound.
A stingray's venom is not necessarily fatal, but it can hurt a lot. It contains various enzymes and the neurotransmitter serotonin, which causes severe muscle contraction, resulting in severe pain.
The enzymes cause tissue and cell death. If the venom is in an area like the ankle, it can usually be treated. Heat breaks down stingray venom and limits the damage it can do. If the wound is not treated quickly enough, amputation might be necessary.
But if the venom enters the abdomen or chest cavity, the resulting tissue death can be fatal because of the major organs located there.
If the spike enters the heart, as was in Australian TV personality Steve Irwin's case, the results are typically fatal.
Source: HowStuffWorks website