private void freeParticle(int idx) {
        Particle p = particles[idx];
        p.life = 0;
        p.size = 0f;
        p.color.set(0, 0, 0, 0);
        p.imageIndex = 0;
        p.angle = 0;
        p.rotateSpeed = 0;

        if (idx == lastUsed) {
            while (lastUsed >= 0 && particles[lastUsed].life == 0) {
                lastUsed--;
            }
        }
        if (idx < firstUnUsed) {
            firstUnUsed = idx;
        }
    }
Kills the particle at the given index.

@param index The index of the particle to kill
@see #getParticles()
jme3-core/src/main/java/com/jme3/effect/ParticleEmitter.java