Musser's fiancée, Paige Press, revealed the news on her Instagram Stories on Saturday. She shared photos of herself and Musser, writing on top, via Entertainment Tonight, "RIP to the love of my life. I will never stop loving you. My heart is broken."
She added: "Today is the worst day of my life. We were so happy. You were the best fiancée I could of ever asked for."
Press also confirmed Musser's death to TMZ, along with his uncle Robert. No cause of death has been shared.
Many fans and friends of Musser shared condolences and memories in the comments section of the late actor's final social media post.
Along with his prominent role in All My Children as a young man searching for his half-sister, Musser is known for a memorable moment in the film Grown Ups, credited as simply "Water Park Stud."
Adam Sandler, who starred in and co-wrote the comedy film, paid tribute to Musser on Instagram, writing, "I loved this guy. Cannot believe he is gone. Such a wonderful, funny good man. Thinking of Alec Musser and his family and sending all my love. A true great sweetheart of a person."
Musser appeared in a few episodes of Rita Rocks in 2009 and in one episode of Desperate Housewives a couple years later.
The late actor and his fiancée raised dogs Calle and Rue together, with the latter being a foster fail. Musser welcomed Rue to the family in June 2022, celebrating the new family member with a sweet video.
Along with acting, Musser did a lot of modeling, particularly in the fitness realm, sharing photoshoot moments on Instagram often. He also appeared to be quite active in activities such as skiing and surfing.