Residents of the Hong Kong district of Tuen Mun on Monday held a demonstration outside police headquarters to protest weird odors emanating from the facility and making people sick.

The odors were thought to be a product of tear gas testing. When the crowd of unhappy residents allegedly committed acts of vandalism, the police responded by spraying them with tear gas.

Coconuts Hong Kong quoted local media reports of residents and school students complaining of strange smells and unexplained illness, including irritated throats severe enough to require treatment by paramedics.

The protest began outside the police facility but moved to nearby Leung Wan Street about an hour later. Police officials said they investigated the reports but could not determine the source of the strange smell and found no evidence of tear gas testing in the area. They wrote a few social media posts urging the demonstrators to disperse, then fired tear gas after a report that a firebomb was thrown at a restaurant.

The Hong Kong Free Press reported on Tuesday that a Bank of China branch was firebombed, but the restaurant, owned by a company “protesters suspect is sympathetic with gangs who have attacked them,” had its front door damaged.

Residents of several nearby buildings complained to the HKFP about the large quantities of tear gas deployed by police contaminating balconies and floating into upper floors of residential buildings. “How did they shoot here?” one bystander asked in disbelief.

In a separate incident on Sunday, Hong Kong police were criticized for bathing a pharmacy and a noodle bar with tear gas. Police officers visited the pharmacy on Monday to apologize for the gassing but could not explain why it occurred.

“I couldn’t do anything else but accept the apology,” the shopkeeper said.