**Core Concept**
Cadaveric spasm, also known as instantaneous rigor or cataleptic rigidity, is a rare phenomenon where muscles contract and stiffen immediately after death, due to the release of catecholamines and subsequent depolarization of muscle fibers. This distinct form of post-mortem rigidity is distinct from the more common rigor mortis, which develops hours after death.

**Why the Correct Answer is Right**
Cadaveric spasm occurs instantly with death, as the sudden release of catecholamines, such as adrenaline, triggers an intense contraction of the affected muscles. This phenomenon is often seen in situations where there is an intense emotional or physical stimulus at the moment of death, such as a violent or traumatic event. The mechanism behind cadaveric spasm is thought to be related to the depolarization of muscle fibers, which leads to a sustained contraction.

**Why Each Wrong Option is Incorrect**
**Option A:** Cadaveric spasm does not typically develop within 2 hours of death, as it is an instantaneous phenomenon that occurs at the moment of death.

**Option B:** 6 hours after death is actually the typical time frame for rigor mortis to develop, not cadaveric spasm.

**Option D:** Cadaveric spasm is distinct from rigor mortis, which develops hours after death due to the breakdown of ATP and subsequent depolarization of muscle fibers.

**Clinical Pearl / High-Yield Fact**
Cadaveric spasm is often seen in situations where there is an intense emotional or physical stimulus at the moment of death, such as a violent or traumatic event. It can provide valuable information to forensic pathologists and investigators about the circumstances surrounding death.

**✓ Correct Answer: C. Instantaneous with death**