Sam Witwicky was the main human protagonist in the first three live-action Transformers movies, and then he was written out of the franchise after Dark of the Moon.

What happened to him

  • In the original trilogy, Sam helps the Autobots repeatedly and becomes a central part of the war against the Decepticons.
  • By the end of Dark of the Moon , he has already finished his biggest story arc, helping defeat the Decepticons and saving Earth.
  • After that, the films stopped following him, and later entries shifted to new human characters instead.

Why he disappeared

  • The real-world reason is that the franchise rebooted its focus, and the later films moved away from Sam and his storyline.
  • Public discussion around the character has often treated him as effectively “gone” from the main film continuity after the third movie.

In-universe status

  • The movies never gave a clear, on-screen death for Sam in the main trilogy continuity.
  • Some later fan discussions and theories try to explain his absence, but those are not confirmed by the films themselves.

TL;DR

Sam did not get a definitive on-screen death in the original movies; he just stopped being the focus after Transformers: Dark of the Moon.