Simplify the following text for a Grade 8 native English-speaking person.
Original: Others , notably first-time sufferers , may even call for emergency services ; many who experience a panic attack for the first time fear they are having a heart attack or a nervous breakdown .
Simplified: Some , notably first-time sufferers , may call for emergency services . Many who experience a panic attack , mostly for the first time , fear they are having a heart attack or a nervous breakdown .