Hit songwriter and producer Michael James Ryan—known professionally as busbee—died on Sept. 29 at the age of 43.

Busbee was diagnosed with an aggressive form of brain cancer over the summer, according to a friend.

Busbee’s songwriting credits include Maren Morris’ “My Church,” Florida Georgia Line’s “H.O.L.Y.,” Keith Urban’s “Fighter,” Garth Brooks’ “People Loving People,” Lady Antebellum’s “You Look Good,” Carly Pearce’s “Every Little Thing” and more.

Busbee also produced and co-produced albums for a number of artists, including Maren Morris, Keith Urban, Lauren Alaina, Lady Antebellum, Carly Pearce and more.

A host of stars reached out via social media to share their condolences.

This just doesn’t seem fair. I will always love you and the songs and albums I was lucky to make with you, Busbee. Rest well, my sweet friend. 💔 pic.twitter.com/9DKsU5G77a

— MAREN MORRIS (@MarenMorris) September 30, 2019

I absolutely can’t accept the loss of mine and Gwen’s friend Michael (Busbee)..Too much to say for social media. Too much pain and unfairness period. I guess sometimes you gotta dig extra EXTRA deep for peace to continue to have faith. And I will because Michael ALWAYS had faith.

— Blake Shelton (@blakeshelton) September 30, 2019

No words. Rest easy my sweet, sweet friend. 💔 @busbee pic.twitter.com/EKA1FVoaIU

— Carly Pearce (@carlypearce) September 30, 2019