Ward question from Season 2: Episode 16.

SPOILERS:

I'm having a rewatch of A.O.S and I've just realised that I've never really understood why Ward shot Thomas Nash, the guy on the Index that was the fake Clairvoyant that Garrett had set up to throw them all off the scent?

Obviously Ward was always in cahoots with Garrett but it's never made sense to me why he supposedly lost control of his emotions and straight out murdered the guy right in front of the whole team?

Was it simply because he was trying to protect Skye (Daisy) as May suggested or was he doing it on Garrett's direct orders? I was always suspicious that when Ward asked Garret if they were "Ringing the bell or knocking", that it was code for going in gently and treating the suspect as friendly or going in hostile and killing them.

I'd love to hear someone else's opinion on this.