A couple were tied up and threatened by a masked gang who broke into their home and used what is thought to be a Taser gun to subdue them.
It is believed a Taser gun was used during the raid
The pair were asleep in their house in Cressing, Essex when the four men broke in on Friday morning.
The 60-year-old man and his wife, 61, were tied up and then the man was given an electric shock.
The gang escaped with a safe containing money and jewellery. Police said the couple had been left deeply distressed.
Det Sgt Greg Potter said: "This is a shocking incident where a frightening amount of violence was used on a couple in their 60s, leaving them deeply traumatised."
The men all wore light-coloured balaclavas and jeans and had local accents.
Taser guns can incapacitate people with a 50,000-volt shock.