Terrible whining sound, what is this horrible sound?

I recently sold my speed3 to a buyer and disclosed known issues, which were just the piston rings on cylinders 1 and 2 being worn (not terribly) and the ac being out. This was all I knew of at the time.

3 days later, he sends me this video with permission to ask the question here. It is a horrendous sound! The turbo had showed no signs of failure prior to sale and had been making great boost, no noises, no leaks, no smoking. Suddenly (overnight) it started making this sound after being parked outside.

My guess was either a really bad boost leak or the turbine hitting the housing. What do you guys think?

Appreciate the help.