<human>: If anyone could win an Oscar for acting cool under pressure, I think I could be nominated for today. An employee of mine started acting a little off while helping a customer but nothing alarming. Then less than 5 minutes later, he disappeared into the kitchen and immediately ran out of the store without his shirt on. To be fair, our AC unit in the store was not working today, so it was slightly warm. It was warm but not unbearable, maybe 85 or so? 

He's outside without a shirt on and he keeps pacing around the sidewalk flailing his arms around meanwhile the customer and I are confused and asking him what he's doing. He says he thinks he's over heating so I offer him water and tell him to sit and rest. He then says he can't feel either of his arms and that we should call his mom. While on the phone with his mother, he yells to call an ambulance. Taking the dispatcher's instructions, I sit him down on a chair in front of a freezer until the EMTs arrive. This kid is shivering and looks completely panicked. I felt so bad but also completely responsible for his well-being until they showed up. They got there less than 5 minutes later and immediately took a blood sample and hooked him up to a portable drip. 

Talking to his mother, it turns out he's had some kind of heart issue in the past but I don't know what. He went to the hospital in an ambulance. I am still in shock. I felt more adult in this 15 minute event than I've collectively ever felt.

Can you summarize the given text in a few sentences?
<bot>: An employee at work needed immediate medical attention which became my responsibility to keep him calm, alert, and stable until said medical attention arrived. It was a humbling and eye-opening experience that made me feel uber-grownup.