5:55 PM PT -- Special prosecutor Erlinda Ocampo Johnson, who resigned during Friday's hearing, tells TMZ ... "As prosecutors we have obligations to disclose all the evidence. When I learned this morning of the existence of the evidence that had not been disclosed, I believed that the right decision was to dismiss the case. When my voice was not heard, I asked to withdraw from the case. We not only owe a duty to the people, but to the defendants accused of crimes as well. The prosecution must always be above reproach."

4:50 PM PT -- Special prosecutor Kari Morrissey gave a statement to reporters saying, “I believe that the importance of the evidence was misconstrued by the defense attorneys."

She continued, “But I have to respect the court’s decision.”

It's a stunning turn ... Alec Baldwin's manslaughter trial has come to an abrupt end as the judge dismissed the "Rust" case after finding law enforcement had concealed evidence that prevented the actor from preparing his defense.

Baldwin broke down in tears, as did his wife, Hilaria, as it became apparent the judge was dismissing the case. Baldwin faced up to 18 months in prison if convicted in the death of "Rust" cinematographer Halyna Hutchins, so the turn of events is incredibly dramatic.

Baldwin's attorney, Alex Spiro, claimed authorities intentionally concealed evidence of live ammo on the set.

Police investigator Marissa Poppell testified she had been instructed by her superiors to create a report documenting that police had received ammunition and to file it under a different case number than the "Rust" case. In other words, it wouldn't be visible to the defense.

Live ammunition on the set is a critical part of the case and could have helped Baldwin argue those around him were responsible for loose safety standards.

The judge found hiding critical evidence hampered Baldwin's ability to defend himself, and the only appropriate sanction was to dismiss the case with prejudice. The judge said, "There is no way for the court to right this wrong."

One of the prosecutors in the case, Erlinda Ocampo Johnson resigned in the middle of Friday's hearing over the alleged cover-up of evidence.

In a dramatic scene in court, the judge put on a pair of blue surgical gloves and sliced open a bag of evidence handed to her inside a manila envelope ... evidence that Baldwin's team claimed they had not seen until that point.

We've reached out to Baldwin's attorney Alex Spiro for comment. So far, no word back.