Answer:
A panic attack
Explanation:
A panic attack is a psychological mental state. It occurs instantly and creates a problem for a person. It creates several physical symptoms. It is a very intense and frightening condition. When it occurs it creates a problem like it seems a person has a heart attack.
Many people in their life face this from one or two times. If a person has a panic attack and this condition consistent for a long time and it seems like a heart attack. The person feels like again face panic attack is called panic disorder.
Thus here Bert's condition in the mall reveals that he was suffering from a panic attack, not a heart attack.