Solar hits, Death Saving Throw at start or after damage reduction?

Solar HITS w/ Slaying LB on a 101~HP target, Death con saving throw req. start with the HIT or after damage reduction? @JeremyECrawford

— Joshua Frost (@Miztuh_J) January 4, 2017

Slaying Longbow sequence:
1. Hit
2. Deal damage (apply any resistance)
3. Make saving throw if the target has hit points ≤ 100 #DnD https://t.co/AxDnx4ZUzL

— Jeremy Crawford (@JeremyECrawford) January 4, 2017