How can I have tapered path in WPF XAML?

Question

I have a Path shape defined in XAML as following :

<Path Stroke="Gray" StrokeThickness="52" x:Name="theCurve">
    <Path.Data>
        <PathGeometry>
            <PathGeometry.Figures>
                <PathFigureCollection>
                    <PathFigure StartPoint="10,100" x:Name="curveStartPoint">
                        <PathFigure.Segments>
                            <PathSegmentCollection>
                                <BezierSegment Point1="100,10" Point2="200,200" Point3="300,100" x:Name="curveBezierSegment"/>
                            </PathSegmentCollection>
                        </PathFigure.Segments>
                    </PathFigure>
                </PathFigureCollection>
            </PathGeometry.Figures>
        </PathGeometry>
    </Path.Data>
</Path>

I want to taper the end of path, check attached image, how can I do that in WPF?