The event attribute makes the selected node and its descendants trigger an arbitrary event when clicked (mousedown/touchstart). This event is triggered on the view itself and the paper. The paper handler is called with the signature cellView, evt, x, y, while the cell view handler is called only with evt, x, y.

element.attr({
  image: {
    // pointerdown on the image SVG node will trigger the `element:delete` event
    event: 'element:delete',
    xlinkHref: 'trash.png'
    width: 20,
    height: 20
  }
});
// Binding handler to the event
paper.on('element:delete', function(elementView, evt) {
  // Stop any further actions with the element view e.g. dragging
  evt.stopPropagation();
  if (confirm('Are you sure you want to delete this element?')) {
      elementView.model.remove();
  }
});