If the matter is as described, that the butcher slaughters the an’aam animal (camel, cow, sheep or goat) as soon as it falls to the ground after receiving an electric shock, if that is done when it is still alive, then it is permissible to eat it. But if he slaughters it after it has died then it is not permissible to eat it. This comes under the ruling on animals killed by a violent blow, which Allaah has forbidden unless they are properly slaughtered before they die. The slaughter does not count unless it is proven that the animal showed signs of life such as moving a leg or if blood flowed (at the time of slaughter) and so on, which indicates that it was still alive until the slaughtering was over. Allaah says (interpretation of the meaning): 

“Forbidden to you (for food) are: Al‑Maitah (the dead animals — cattle — beast not slaughtered), blood, the flesh of swine, and that on which Allaah’s Name has not been mentioned while slaughtering (that which has been slaughtered as a sacrifice for others than Allaah, or has been slaughtered for idols) and that which has been killed by strangling, or by a violent blow, or by a headlong fall, or by the goring of horns — and that which has been (partly) eaten by a wild animal — unless you are able to slaughter it (before its death)”

[al-Maa'idah 5:3]  

An’aam animals that have been exposed to a fatal blow are permissible so long as they are slaughtered properly before they die, otherwise it is not permissible to eat them.