The canonical example for a speech act that can cause real harm has long been “screaming ‘Fire’ in a crowded theatre”. Maybe this should be replaced with “screaming ’suicide bomber’ in a packed crowd”.
All in all, last week has been rather too murderous.
(I am aware that neither of these utterances is a performative act the consequences of which follow by virtue of its being spoken. Like declaring a convention open by virtue of someone in charge saying “I declare this convention open”. The one thousand or so pilgrims didn’t die from the words “there’s a suicide bomber in the crowd” merely being spoken, but of the physical acts that ensued.)