Jack Osbourne got emotional revealing how he learned his father Ozzy Osbourne had suddenly passed.

He opened up about the heartbreaking moment in a YouTube video posted on his channel Wednesday … revealing a person who had worked for his family for 30 years came knocking on the door of his Los Angeles home at 3:45 in the morning to tell him the sad news.

Jack — visibly holding back tears — said he immediately felt “sad and frustrated and angry” over Ozzy’s passing, but felt comforted knowing his father was no longer suffering.

The Black Sabbath legend died of a heart attack on July 22 … he also suffered from coronary artery disease and Parkinson’s disease.

Jack said his father “was having a rough go” before he died, noting fans could see that at his farewell show with his heavy metal band on July 5. Despite this, he said no one expected his death “to happen as quickly as it did and when it did.”

At another point in the video, the reality star and paranormal investigator said he’s grateful he spent extra time with Ozzy before he passed, thanks to his kids getting hit with the stomach flu.

He said they were supposed to embark on a family trip to Portugal before they got sick, but that was canceled and they stayed in England longer.

Jack broke his silence on the “Crazy Train” rocker’s death at the beginning of August, saying he was sorrowful over his loss, but thankful he got to call him his father.

Jack’s continued to honor him by sporting Black Sabbath merchandise, and even hitting back at haters — namely Pink Floyd’s Roger Waters, who dragged Ozzy’s legacy through the mud in a recent interview.