UnitedHealthcare CEO Shooter's Possible Jacket Flying Off Shelves After Sleuth Speculation

Internet sleuths believe they have found the jacket worn by the gunman who killed UnitedHealthcare CEO Brian Thompson ... and now it is morbidly flying off the shelves.

On Reddit, a user speculated the suspect's jacket was a Sherpa Lined Two Picket Hooded Trucker Jacket by Levi's ... sold at Macy's for the retail price of $225.

The jacket's popularity has since spread like wildfire on the company's website ... where more than 6,000 people were viewing the jacket at the same time -- and nearly 700 were sold in the past 48 hours, according to an item popularity tool on Macy's site.

As you know, Thompson was fatally shot in Manhattan on Wednesday ... and the nationwide manhunt for his killer continues.

NYPD Chief of Detectives Joseph Kenny told reporters Friday that detectives are looking into the possibility the gunman used a veterinary gun ... a larger gun commonly used on ranches and farms -- but the gun hasn't been recovered.

However, a backpack suspected of belonging to the shooter was found in Central Park. As TMZ reported ... the backpack appears to be an Everyday Backpack from Peak Designs ... a bag meant for serious photographers but designed for casual use, also.