EVENTS NEVER turn out like you expect.  Not long ago , we answered a call that came to us from dispatch as a "bicyclist down." We get a lot of these calls. But as the engine was pulling up to the scene, the captain, seated in the right front seat, could see a bystander performing CPR on the bicycle victim.

A nagging question has emerged in the wake of the death of NBC’s Tim Russert. Where was the defibrillator?

NBC News has declined to comment on whether an automated external defibrillator, or A.E.D., was nearby at the time of Mr. Russert’s collapse or why a defibrillator wasn’t immediately used. Cardiac arrest typically is caused by a chaotic heart rhythm called ventricular fibrillation, which can be restored to normal if treated early with electric shock. Many public spaces, including airports, casinos, office buildings and even golf courses, are now equipped with A.E.D.’s, which are the only real hope for surviving a cardiac arrest. An A.E.D., which is about the size of a laptop computer, is a computerized device that analyzes the heart rhythm and prompts even an untrained rescuer to deliver an electrical shock if needed.