If a Watchful Sentry is killed during a showdown, triggering Deathknell to draw Hex Tech Ray, can you use Hex Tech Ray to kill the attacking unit before combat damage is dealt?

Ruling: Yes, you can use Hex Tech Ray to kill the attacking unit before combat damage is dealt.

Sequence:

• Showdown occurs and Watchful Sentry is killed
• Deathknell triggers and you draw Hex Tech Ray
• You can play Hex Tech Ray before combat damage step
• Combat damage step only happens after the showdown is over