Other electric currents passing through your body during electrocution can fool your muscles into contracting very strongly. This is dangerous because your hands could become 'stuck' when holding onto the source of electricity that is giving you the electric shock. This would make matters much worse for you as it would allow more and more electricity to affect your body. You're more likely to be thrown away from the source, but that's not certain. On the other hand, and this is what the Tesla-Edison arguement was about, safe low voltage AC can be transformed into a dangerous high voltage supply.
All electricity has some dangers even a battery can cause a fire in the wrong circumstances.