Kourtney Kardashian recently became engaged to Blink 182 drummer Travis Barker.
But her ex and father of her three children, Scott Disick, isn't happy about it.
"Scott is going crazy," an insider told Page Six. "He's going to go off the deep end. It's really bad. It's about to get dark."
Another source told People, "Scott never approved of Kourtney dating Travis. He has struggled with their relationship. He always had this idea that he and Kourtney would eventually get back together. He was pretty shocked when he found out that she was dating Travis."
Scott has dated lots of young women since splitting from Kourtney, including Sofia Richie and Amelia Hamlin.
Travis had been planning his proposal to Kourtney for some time.
"Travis told her family that he planned to propose, but everyone was great at keeping it secret," the insider said. "The Rosewood is their favorite for short weekend getaways. They often stay at the hotel. This is why Travis proposed there. It's a very special place to them, but it was also easier to keep everything a secret by proposing there."