I've added a simple extra column to the grid. How do I know what column the menu is dropped down for?

Code:
columnMenu: {
        xtype: 'menu',
        align: 'tl-bl?',
        hideOnParentHide: false,
        items: {
            remove: {
                iconCls: 'x-fa fa-trash',
                text: 'Remove',
                handler: function (item) {
                    // how do I get the index of the column I clicked the menu for?
                    item.up('grid').fireEvent('deleteColumn', item);
                },
            },
        },
    },