Detective Inspector Louise Ludwig said: "We would urge all shoppers to be wary of anyone who might be watching you at the checkout.
"Always cover your PIN when you enter it into a cash machine or Chip & PIN machine at the tills.
"Try to avoid being distracted by people asking for directions, and keep your valuables safe."
More top news
Essex Police say that they can't comment on Martin Goldberg's death, but there were indications of an attempt to destroy evidence.
Police say indecent images of children have been found at the home of a deputy head teacher, who was recently found dead.
Essex Police say pictures of boys undressing have been discovered in the home of a teacher who's been found dead.