In reaction, the robber hastily fired a shot as he rushed out of the shop. Another random shot was fired to scare off passers-by as the four armed men fled on two motorcycles.
An acid-laced glove and two bullet casings were later found by policemen investigating the 11.30am robbery yesterday.
State Crime Investigation chief Asst Comm Raja Shahrom Raja Abdullah said that any clinic or hospital where a patient had sought treatment for acid burns should alert the police immediately.
There were no other casualties and the losses incurred in the robbery had yet to be determined.
From initial investigations and CCTV footage, ACP Raja Shahrom said based on their size and movement, the men were estimated to be below the age of 30.