"His friend died from a heart attack."
Translation:그의 친구가 심장마비로 사망했어요.
죽다 vs 사망하다
죽다 - pure Korean word
사망하다- word with chinese root.
죽다 - die, die down, fade away
사망하다 - lose one's life, be killed, pass away etc.
사망하다 only applies to humans and is considered more formal than 죽다.
죽다 applies to all things. e.g.
추억은 죽었다 - memories died/faded.
불이 죽어요 - the fire dies down.
사망하다 cannot be used in such cases.