Kelly Osbourne is mourning the loss of her "best friend" and father Ozzy Osbourne.

On Thursday (July 24), Kelly broke her silence on her dad's death two days after the legendary musician passed away at the age of 76, sharing a poignant lyric from her dad's 1972 song "Changes," a track he co-wrote with his Black Sabbath bandmates that features on the band's album Vol. 4, on her Instagram Stories, per People.

"I feel unhappy I am so sad," she wrote, alongside a heartbreak emoji. "I lost the best friend I ever had."

The song choice held an even more personal connection to the 40-year-old TV personality, as she and Ozzy recorded another version of the song together as a duet with revised lyrics in a single that came out in 2003.

A statement shared by his family — including Kelly, his wife Sharon and sons Louis and Jack — confirmed that the "Crazy Train" singer passed away July 22.

"It is with more sadness than mere words can convey that we have to report that our beloved Ozzy Osbourne has passed away this morning," the statement reads. "He was with his family and surrounded by love. We ask everyone to respect our family privacy at this time. Sharon, Jack, Kelly, Aimee and Louis."

Condolences and remarks from fans all over the world poured in after news of his death, with fans and friends paying tribute to the Prince of Darkness. Bands like Coldplay and artists like Alice Cooper and Lady Gaga also honored the late rocker with live performances and homages to his legacy.