You can only select and shatter the items you recently touched and intend to shatter. For example, if you give someone a hand shake, and you touched a crow bar, and you intend to shatter the crow bar and not the hand of the person you gave the hand shake to, you will only shatter the crow bar and not the hand. Every item you ever shatter will be intentional and never accidental. It's only limited to what you intend to shatter. Your ability is not involuntary or accidentally committed. ...and yes, you can select multiple items.