Amber Marshall is mourning her Heartland costar and on-screen love interest, Robert Cormier, after his unexpected death at age 33.

On Wednesday, Marshall shared a touching tribute to her late costar on Instagram, featuring photos of them together on the set of the long-running family drama series.

As fans may know, Marshall plays protagonist Amy Fleming on the show while Cormier played Finn Cotter, a character that was introduced in season 15 as a potential love interest for Amy.

“Robert was truly a joy to be around. He had an infectious smile, and such a big heart. He was especially kind and gentle with the animals on set, which goes a long way in my books,” Marshall, 34, wrote in the caption of her post.

“Robert, I am so thankful I was able to get to know you and work alongside you. You left us far too soon, but I promise you will always be remembered. #RIP” she added.

Cormier died on Friday, according to his obituary. His sister Stephanie later told The Hollywood Reporter that Cormier died in a hospital in Etobicoke, Ontario, due to injuries sustained in a fall.

“Robbie was loved by many and his unexpected death has left us devastated,” the family said in a statement to PEOPLE on Wednesday. “While we are broken-hearted, we take comfort in the overwhelming love and support shown to our family by Robbie’s friends, colleagues and fans.”

“Robbie passed away as the result of a tragic accident,” the family continued. “Our family would like to thank everyone at the Critical Care team in Toronto for the compassionate care they provided Robbie and the kindness they showed our family. We will be forever grateful.”

The family also asked for privacy as they continue to grieve Cormier’s death.

In his obituary, Cormier was remembered as “an athlete, an actor, and a great brother.”

“He had a passion for helping others and was always looking to achieve more. He enjoyed movie nights with his family, and looked up greatly to his father,” the obituary read. “He impacted many people throughout his life whether it was family, teammates and friends.”

The obituary continued, “Rob’s memory will live on through his passion for art and film; as well as his three sisters who meant the world to him.”