"According to investigators it appears that the scene being filmed involved the use of a prop firearm when it was discharged," a Thursday release from the sheriff's office said. "Detectives are investigating how and what type of projectile was discharged."
USA TODAY obtained an email sent to members of IATSE Local 44, a union of prop makers and other craft persons who work within the entertainment industry, about the incident. The message said the prop gun from the "Rust" set was loaded with "a live single round" and that no Local 44 members were on set.
"As many of us have already heard there was an accidental weapons discharge on a production titled 'Rust' being filmed in New Mexico. A live single round was accidentally fired on set by the principal actor," the email read.
The incident is still under active investigation, the sheriff's office said. Detectives are continuing to interview witnesses.
"There are no words to convey my shock and sadness regarding the tragic accident that took the life of Halyna Hutchins, a wife, mother and deeply admired colleague of ours," he said in a series of tweets Friday.
"I'm fully cooperating with the police investigation to address how this tragedy occurred and I am in touch with her husband, offering my support to him and his family."