Serge Svetnoy just filed suit against the above-mentioned individuals -- as well as others -- claiming the defendants' alleged negligence caused him severe emotional distress in the aftermath of it all.

According to the docs, obtained by TMZ, Svetnoy claims the bullet that struck both Hutchins and director Joel Souza actually zoomed by and nearly hit him too. Not just that, but the gaffer claims he was one of the first people on hand to tend to Halyna while she was profusely bleeding ... attempting to comfort her and keep her conscious.

As for why he's suing Baldwin, the suit claims he "owed a duty to the Plaintiff and other crew members and actors on the 'Rust' set to handle the Colt Revolver provided to him by defendant Halls with reasonable care and diligence for the safety of 'Rust' cast and crew." It goes on to say, "This duty called for Defendant Baldwin to double-check the Colt Revolver with Halls upon being handled to ensure that it did not contain live ammunition."

And, it goes on ... "This duty further called for him [Baldwin] to handle the Colt Revolver as if it was loaded and to refrain from pointing it at anyone." In other words, the suit claims negligence on Baldwin's part.

And, there's this ... according to the lawsuit, the scene Baldwin was rehearsing did not call for him to pull the trigger. According to the lawsuit, the scene called for Baldwin to draw the gun and point it in the general direction of the camera, but, "the scene did not call for Defendant Baldwin to shoot the Colt Revolver."

The suit also claims Baldwin was negligent as a producer on "Rust," saying, "... they attempted to save money by hiring an insufficient number of crew members to safely handle the props and firearms ..." It goes on to claim there were other lapses on the set, including violating industry norms, declining requests for weapons training days, failing to allow proper time to allow for gunfire, failing to send out safety bulletins and spreading the staff too thin.

The suit also claims the target practice that was going on shortly before the tragedy was "outrageous."

Svetnoy says he'd known Halyna for 5 years and considered her a good friend.

The ordeal was absolutely traumatic, so says Svetnoy, and has since left him in utter mental anguish ... to the point he feels he might not ever be able to get over it.