Both Baldwin and armorer Hannah Gutierrez-Reed face two counts of involuntary manslaughter. They will be "charged in the alternative," meaning a jury will decide not only if they are guilty, but under which definition of involuntary manslaughter they are guilty. To be found guilty of the first charge, involuntary manslaughter, the D.A.'s office must prove there was underlying negligence. The other charge is involuntary manslaughter in the commission of a lawful act, which requires proof that there was more than simple negligence involved in a death. Celebrity attorney Chris Melcher explains to Yahoo Entertainment what this all means.

"The decision to file involuntary manslaughter charges against Baldwin and Gutierrez-Reed is supported by their failure to follow basic rules for firearm safety. The first safety rule required Baldwin to treat the guns as being loaded until it was physically checked in his direct presence to confirm that no live rounds were in the gun. This happens every time before a gun is handed to an actor on set," Melcher says. "Baldwin accepted the word of the first assistant director, David Halls, that the gun was not loaded, even though Halls was not authorized the handle the gun and no one showed Baldwin that the gun was safe. It was reckless for Baldwin to take the word of an unqualified person that the gun was not loaded and then point it at Halyna Hutchins."

Halls has agreed to plead guilty to negligent use of a deadly weapon. The terms include a suspended sentence and six months of probation. Melcher calls this a "good move" because "he was likely to be convicted."

"My sense is that he took the guilty plea to reduce his exposure to jail or prison time. The prosecution did not need Halls's cooperation to secure a conviction against Baldwin. We know what happened on the set because statements have been provided. The facts are not really in dispute. The question is whether a jury will conclude that those facts are enough for a conviction," he notes.

If this goes to trial, Baldwin's version of events will be scrutinized by experts. The 30 Rock star said he did not pull the trigger. Baldwin, who blamed Halls, Gutierrez-Reed and other crew members for Hutchins's death in his own legal filing, said he pulled back the hammer during rehearsals at the cinematographer's request, but not far enough to actually cock the gun.

"The prosecution will need to call a firearms expert to testify that the gun was tested and did not fire without the trigger being depressed," Melcher says.

Under New Mexico law, involuntary manslaughter is a felony punishable by up to 18 months in jail and a $5,000 fine. The first charge also includes the misdemeanor charge of negligent use of a firearm, which would likely merge as a matter of law.

Involuntary manslaughter in the commission of a lawful act is also a fourth-degree felony punishable by up to 18 months in jail and up to a $5,000 fine. However, this charge includes a firearm enhancement, or added mandatory penalty, because a firearm was involved. The firearm enhancement makes the crime punishable by a mandatory five years in jail.

Melcher explains: "The prosecutor will file several charges, ranging from the negligent use of a firearm, which could carry no jail time, to involuntary manslaughter involving the use of a firearm, which requires a five-year mandatory prison sentence. Alec may be able to plea bargain for the lower charges to accept responsibility without serving time in jail."

As for whether a plea bargain is in Baldwin's best interest, high-powered California criminal defense lawyer, Michel Huff, tells Yahoo it depends.

"Obviously, we would need to see the terms of the plea offer, but I suspect that any deal requiring prison time for Baldwin would be rejected," Huff, who has tried cases for 26 years, explains. "While a lengthy, public trial is not likely in the actor's best interests, given his considerable resources, Baldwin would be able to fight the charges tooth-and-nail and may have a good chance of coming out on top."

As of now, it sounds like Baldwin has no interest in accepting any responsibility.

"This decision distorts Halyna Hutchins's tragic death and represents a terrible miscarriage of justice," the actor's attorney, Luke Nikas of Quinn Emanuel, told Yahoo on Thursday. "Mr. Baldwin had no reason to believe there was a live bullet in the gun – or anywhere on the movie set. He relied on the professionals with whom he worked, who assured him the gun did not have live rounds. We will fight these charges, and we will win."

Lawyers for Gutierrez-Reed, who was in charge of weapons on set, also said she "will be exonerated of wrongdoing."

"Hannah is, and has always been, very emotional and sad about this tragic accident. But she did not commit involuntary manslaughter. These charges are the result of a very flawed investigation, and an inaccurate understanding of the full facts," Jason Bowles and Todd J. Bullion said in a statement on her behalf. "We intend to bring the full truth to light and believe Hannah will be exonerated of wrongdoing by a jury."

The charges will be officially filed by New Mexico First Judicial District Attorney Mary Carmack-Altwies before the end of the month.

"After a thorough review of the evidence and the laws of the state of New Mexico, I have determined that there is sufficient evidence to file criminal charges against Alec Baldwin and other members of the Rust film crew," Carmack-Altwies said on Thursday morning. "On my watch, no one is above the law, and everyone deserves justice."