How to stop extjs treepanel from loading infinitely?

Finally after struggling with extjs tree panel, tree store and building custom reader to read and convert pentaho data for 2 weeks I have managed to load pentaho data into treepanel of extjs.

Now my Tree panel is loading same data infinitely. Treepanel looks as follows :

Part of my json data looks as follows :

{
    {name: 'US', candidateCount: 3, children: []},
    {name: 'India', candidateCount: 922, children: [
       {name: 'Goa', candidateCount:124, children: []},
       {name: 'Maharashtra', candidateCount: 43, children: [
             {name: 'Pune', candidateCount: 3},
             {name: 'Mumbai', candidateCount: 33},
             {name: 'Kolhapur', candidateCount: 4},
             {name: 'XXX', candidateCount: 3},
        ]}
     ]},
    {name: 'UK', candidateCount: 1, children: []},
}

As you can see in image above, after expanding India node it has again loaded data of country level (i.e. country names US, uk, India, UK). Actually I want to show state level data like data of Maharashtra, Goa. Instead of that treepanel is again loading same data again.

How to avoid this kind of behavior? I have already set leaf property of US, uk and India nodes to false.

I tried setting Expanded property to true but then treepanel keeps loading same nodes again and again and my browser tab just gets hanged.

Please let me know how to avoid this? I want tree panel to load data only once.

---

EDIT - Solution to this problem

I solved this problem by adding listener on append event of store and then setting leaf value to true for the nodes which I wanted to be leaf.

Setting data item to:

{
    ...
    leaf: true
}

will stop it.