Il s'approcha; puis il a disparu
You usually use the same tense in such sentences:
→ Il s'est approché, puis il a disparu !
→ Il s'approcha, puis il disparut !
Jojo, when should we use the 2nd sentence?
I'm not Jojo, but this is the past historic tense which is used in literary situations; it is usually seen in books, but not spoken, except in some French dialects.
I believe that is the passé simple. It's basically the literary equivalent of the passé composé.