Expose additional data based on xAxis element click – Highcharts.js

I’m facing some difficulties while trying to implement ‘xAxis clickable’ column chart. I’m trying to expose additional Pie charts below my column chart, based on user click on one of the element in xAxis.

enter image description here

The way the first graph is build:

function chartBuilder(data) {

            if (data.length === 0) {
                return null;
            }

            var categories = [];
            var uniqData = [
                {name : 'Fatal', data:[], color:'black', stack: 'fatal'},
                {name : 'Critical', data:[], color:'red', stack: 'critical'},
            ];
            _.each(data, function (item) {
                categories = categories.concat(item.site);
                var fatalValue = {};
                fatalValue[item.site] = parseFloat(item.fatal || 0);
                uniqData[0].data = uniqData[0].data.concat(fatalValue);
                var criticalValue = {};
                criticalValue[item.site] = parseFloat(item.critical || 0);
                uniqData[1].data = uniqData[1].data.concat(criticalValue);
            });

            var chartConfig = util.basicConfigChart(categories, uniqData);
            chartConfig.yAxis.title = {
                text: 'Num Of Events'
            };
            chartConfig.xAxis.labels = {

                formatter: function() {
                    var ret = this.value,
                        len = ret.length;

                    if (len > 10) {
                        ret = '<strong>' + ret.slice(0,ret.indexOf('_')) + '<br/>' + ret.slice(ret.indexOf('_') + 1, len) + '</strong>';
                    }

                    if (len > 25) {
                        ret = ret.slice(0,25) + '...';
                    }

                    return '<strong>' + ret + '</strong>';
                },
                useHTML: true
            };
            chartConfig.options.tooltip = {
                formatter : function () {
                    return '<strong>' + this.series.name + '</strong>:' + this.point.y + '<br>Total: ' + this.point.total;
                }
            };
            return chartConfig;
        }

So basically, what I need is a way to determine which element in xAxis was clicked, and expose below pie charts with data relevant to this element.

Source: AngularJS