Seperation anxiety hits close to home for me.. we had a 5 year old pitbull who developed it and unfortunately it was not a good outcome. I struggled with whether or not I wanted to post about it but I decided to.
He developed it pretty much out of nowhere a couple of years after we adopted him. He was such a great dog, he was always ok being on his own, the one say it's like he just.. snapped. He went through window screens if my mom was down the road chatting to a neighbour trying to get to her.. he would whine and literally SCREAM when my mom went out.. we had several neighbours stop by to ask if he was ok and make sure we weren't torturing him because it sounded so horrific. He tore up the house every time he was left alone for anywhere between 10 mins to a full work day (by tore up I mean ripped up couch cushions and chewed up remotes/phones/coffee tables etc) I can tell you we tried EVERYTHING with our baby to make him better... spent thousands of dollars on vet trip, behaviourists, training, medications.. he just wouldn't get out of it. We crated him but he was so desperate to get out he BENT THE BARS on the crate and cut himself up in the process.. he just wouldn't snap out of it. One of the worst things he did was once when my mom brought him with her to go drop papers off at her workplace she left him in the cab of the truck for 2 minutes with the window cracked 2 inches.. she came back and her window was smashed and he was wandering around the workyard searching for her and he was bloody from cutting himself up on the broken window.
One day while my mom was out grocery shopping he was left home alone for an hour. She came back and he tore off the pads on his feet going crazy
He tore down door frames, window frames, tore up and ripped carpetting all over her house, scratched doors and walls.. there was blood everywhere.. it was terrible. There were bloody streaks all over the walls and stained carpets
Anyway we consulted a couple of vets and my moms friend who works at our local animal rescue about making a final decision and after a year of trying to resolve his seperation anxiety issues unsuccessfully he had to be put down
Rehoming wasn't an option because his actions wouldnt change and we didn't want to give him to someone and find out they dropped him off at some shelter because they couldn't 'fix' him either. I miss him so much, he was such a great dog.. I wish we knew what happened to our poor baby.
One tip that sticks out that a behaviourist told us to do was to fill up a garbage bag with paper and 'pretend' to take it out a few times a day to get your dog used to you going and coming back so they understand you are not and will not abandon them. It's worth a shot.. it helped our baby out at the beginning before he went out of control.