We're sad to report that Dave Mustaine's mother-in-law, Sally Estabrook, has been reported missing. The 75-year-old, who suffers from Alzheimer's disease, was last seen at the Pinezanita RV Park & Campground in Julian, Calif., on Oct. 4.

Estabrook's husband noticed his wife was missing after he returned from taking a shower. He quickly called the sheriff's department. Throughout the weekend, a search and rescue team combed through the 26.5 acre area, finding no trace of Sally Estabrook.

The woman is 5'4" tall, weighs roughly 145 pounds, had shoulder-length blonde hair and was wearing a teal top and white capris pants the day she went missing. Estabrook is reportedly uncommunicative, but may respond to her name.

Earlier today, Mustaine asked fans to send positive thoughts in the following Tweet:

The Megadeth frontman's daughter Electra has been sending out a large number of tweets asking for help from anyone who can provide it:

Mustaine actually spoke with us about his mother-in-law's affliction during a 2013 interview:

Until it happens to you, you really have no idea. And I think that when I saw how upset our family became and yet how we are able to provide the resources for her, it made me think about all the families going through this that don’t have the resources to take care of a loved one. It also made me really appreciate our fans because without them I would not be able to take care of things the way I am. Really brings it all home. And then beyond that, like I said, I just did what any good artist does. I put my emotions into my music. That’s the pain you hear in the music. It’s real. People can say, “We don’t want to hear this kind of s–t,” but to me, this s–t is important.

If anyone has information about Sally Estabrook, please call 911 or the local sheriff's department at (858) 565-5200.

Sally Estabrook Report