Why are capacitors dangerous?

A capacitor is a device used in most electronic devices to store electric charge in order to keep the system functioning. If for example a television was in used for a few hours and then shot down, if aTechnical has to perform some hardware services on the device due to some malfunctions, He needs to handle the capacitor with care or have it discharged before touching it with his bare hands, otherwise he stands the risk of electric shock and consequently death.