A call of a person with a mask at a Walmart Supercenter in St. Charles prompted a police response and evacuation at the store, but police later said the man involved was a heart transplant survivor wearing a "medical device" while grocery shopping with his mother.
St. Charles police said they received a call of a person wearing camouflage and a mask, sparking security concerns at the Walmart at 150 Smith Rd.
"It was reported that a male subject entered the store wearing a mask concealing his face," police said in a statement. "Wal-Mart management took precautionary measures and evacuated the store."
Police later said the man who prompted the call was wearing an oxygen mask following a heart transplant and evacuated the store with the rest of the shoppers.
"It was determined that the subject was wearing a medical device due to recent medical treatment," police said. "There was no criminal activity involved in the incident."
Police said there was no threat to the public.
The incident comes days after 22 people were killed at a Walmart store in El Paso, Texas. Numerous other incidents have been reported at Walmarts across the country, including earlier this week in Bedford Park, Illinois.
Police were called to the Walmart Supercenter in at 7050 S. Cicero Ave. Tuesday evening after several calls of shots fired. A shell casing was found near an intersection outside the store but police said there was no evidence of a shooting or gunman inside the building.
Panicked shoppers also fled a Walmart in Springfield, Missouri, Thursday after a man carrying a rifle and wearing body armor walked around the store before being stopped by an off-duty firefighter. No shots were fired and the man was arrested after surrendering, Springfield police said. No one was injured.
Check back for more on this developing story.