The Supernatural alum, 43, paid tribute to Hutchins, 42, in an Instagram post on Sunday, sharing behind-the-scenes photos of her riding horses and posing with the cast, including himself, Alec Baldwin, Josh Hopkins and Travis Fimmel.
"This has been a tragedy of epic proportions that we are all still processing," Ackles began.
"Earlier last week I felt compelled to tell Halyna just how awesome I thought she was," he continued. "I told her how incredible I thought her camera shots were and just how exciting it was to watch her and her team work. Truly. She laughed and said thank you and gave me a hug. I'll forever be thankful we had that moment. She had a spunk and passion that infected the entire crew from the top down."
"She was an inspiration," Ackles added. "My heart and prayers go out to Halyna's husband, son and the rest of her family. There just aren't enough words to express what an immense loss this is. She will be incredibly missed by all of us who knew and admired her."
In the wake of the tragedy, Hopkins, 51, also shared fond memories of Hutchins on Saturday.
"As you might imagine, the entire cast and crew are in a state of absolute surreal grief and shock and I want to thank everyone who has reached out with such beautiful support and love," the Cougar Town actor wrote. "Secondly, there is already so much hurtful, blind speculation and misinformation circulating. Let's please wait for the results of the investigation so we can avoid repeating a tragedy like this ever again."
"Halyna was so generous with her kindness, she was an absolutely lovely person and a fierce artist. Her greatest joy was filmmaking. Please keep her husband, Matthew and their son in your thoughts," Hopkins added.
He also included a link to the GoFundMe launched Friday by ICG Local 600, a chapter of the International Cinematographers Guild, "to help raise funds for her family at this difficult time." As of Sunday, the campaign has raised more than $188,000.
After PEOPLE confirmed that one crew member died and another was critically injured Thursday on the New Mexico set of Rust, the Santa Fe Sheriff's Department said in a statement that Hutchins and writer/director Joel Souza were "shot when a prop firearm was discharged by Alec Baldwin, 63, producer and actor."
Authorities responded to a 911 call from the set at Bonanza Creek Ranch at around 1:50 p.m. local time on Thursday. Hutchins was airlifted to University of New Mexico Hospital where she died of her injuries. Souza, 48, was released Friday from Christus St. Vincent Regional Medical Center where he underwent treatment for his injuries.
RELATED VIDEO: Alec Baldwin Seen Distraught After Accidental Shooting on Set of Rust Movie, Killing Cinematographer
"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," Baldwin wrote Friday in a statement on Twitter.
"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," he continued. "My heart is broken for her husband, their son, and all who knew and loved Halyna."