Interrupt SMS notification sound On our on-call duty phone we receive SMSs from our server monitoring system. The notification tune is quite long and the phone is intentionally loud.

Is it possible to interrupt the tune once it starts playing on iOS 8?

On a previous version of iOS (I can't recall which version this was) it was possible by pushing the On/Off button on the top-right or the Volume Down button on the left.
Yes, using the mute switch for a moment, then put it back to non-muted mode. The volume did used to work, and will still silence calls, but I haven't tried on other alerts of late.

Could be a bug, or issue with your phone. I will try it next time mine goes off, and report back.