Been there with the first filly I bought as a yearling.
She dropped one day at age 20, as the vet was being called
I held her head in my lap, she passed just before the vet
got there, I never cried so hard in my life.
Sad story and I too am surprised this particular horse got spooked.
Sher
Doug & Sher
2006 HR Presidential 34'
2001 Ford Excursion 7.3
Lucy-"Red Fox" Lab...8/7-'07
Bubba,rescue Pom...4/1-2010
Csepki, rescue Poodle...9/15-2001