Laravel Autocomplete not working

I have implemented a Laravel 5.1 autocomplete function using following codes:

snippet js

<script type="text/javascript"> 
 $(document).ready(function () {
  $("#utente").autocomplete({
    minLength:3,
    autoFocus: true,
    source: '',
    select: function( event, ui ) {
        window.location.href = ui.item.url;
    },

});
});

</script>

This is my Route:

Route::any('utente', function(){


 $term = Input::get('utente');
 // 4: check if any matches found in the database table 
 $data = DB::table("tb_users")->distinct()->where('last_name', 'LIKE', $term.'%')->groupBy('last_name')->get();
 foreach ($data as $v) {
 $nome = $v->last_name . ' ' . $v->first_name;
 $url = "clienti?utente=$v->id";
 $return_array[] = array('value' => $nome, 'label' => $nome, 'url' => $url);  }
  // if matches found it first create the array of the result and then convert it to json format so that 
  // it can be processed in the autocomplete script
 return Response::json($return_array);
 });

And this is the fiedl used for rendere the autocomplete.

<input type="text" id="utente" name="utente" placeholder="Cognome e Nome" class="form-control-utente" ></input>

The problem is that this fetch all the results in DB... and not the results that match the query

via Chebli Mohamed