PHQB - works only when chained?

Query builder works only when chained instantly? i cant get working result if i split applying methods to PHQB in different parts of code.

This code works:

        if ($this->request->isPost() && $this->request->isAjax()) {

            switch ($this->request->getPost('type')) {
                case 'getEmergencyCities':
                    $district_id                = $this->request->getPost('district_id', 'int');
                    $result['e_objects_cities'] = Cities::findByDistrictId($district_id)->toArray();
                    $emergency_objects          = $this->modelsManager->createBuilder()->columns([
                        'o.id',
                        'c.value AS city',
                        'a.value AS address',
                        'o.house_number',
                        'o.flats_count',
                        'o.area'
                    ])
                        ->from(['o' => 'Main\Models\EmergencyObjects'])
                        ->join('Main\Models\Addresses', 'o.address_id = a.id', 'a')
                        ->join('Main\Models\Cities', 'o.city_id = c.id', 'c')
                        ->where('o.district_id = :district_id:', ['district_id' => $district_id])
                        ->getQuery()->execute()->toArray();
                    break;

                case 'getEmergencyAddresses':
                    $city_id                       = $this->request->getPost('city_id', 'int');
                    $result['e_objects_addresses'] = Addresses::findByCityId($city_id)->toArray();
                    $emergency_objects             = $this->modelsManager->createBuilder()->columns([
                        'o.id',
                        'c.value AS city',
                        'a.value AS address',
                        'o.house_number',
                        'o.flats_count',
                        'o.area'
                    ])
                        ->from(['o' => 'Main\Models\EmergencyObjects'])
                        ->join('Main\Models\Addresses', 'o.address_id = a.id', 'a')
                        ->join('Main\Models\Cities', 'o.city_id = c.id', 'c')
                        ->where('o.city_id = :city_id:', ['city_id' => $city_id])
                        ->getQuery()->execute()->toArray();
                    break;

                case 'getEmergencyObjects':
                    $address_id        = $this->request->getPost('address_id');
                    $emergency_objects = $this->modelsManager->createBuilder()->columns([
                        'o.id',
                        'c.value AS city',
                        'a.value AS address',
                        'o.house_number',
                        'o.flats_count',
                        'o.area'
                    ])
                        ->from(['o' => 'Main\Models\EmergencyObjects'])
                        ->join('Main\Models\Addresses', 'o.address_id = a.id', 'a')
                        ->join('Main\Models\Cities', 'o.city_id = c.id', 'c')
                        ->where('o.address_id = :address_id:', ['address_id' => $address_id])
                        ->getQuery()->execute()->toArray();
                    break;
            }
            $result['emergency_objects'] = $emergency_objects;
            echo json_encode($result, JSON_NUMERIC_CHECK);
        }

And this doesnt:

if ($this->request->isPost() && $this->request->isAjax()) {

            $emergency_objects = $this->modelsManager->createBuilder()->columns([
                'o.id',
                'c.value AS city',
                'a.value AS address',
                'o.house_number',
                'o.flats_count',
                'o.area'
            ])
                ->from(['o' => 'Main\Models\EmergencyObjects'])
                ->join('Main\Models\Addresses', 'o.address_id = a.id', 'a')
                ->join('Main\Models\Cities', 'o.city_id = c.id', 'c');
            switch ($this->request->getPost('type')) {
                case 'getEmergencyCities':
                    $district_id                = $this->request->getPost('district_id', 'int');
                    $result['e_objects_cities'] = Cities::findByDistrictId($district_id)->toArray();
                    $emergency_objects->where('o.district_id = :district_id:', ['district_id' => $district_id]);
                    break;
                case 'getEmergencyAddresses':
                    $city_id                       = $this->request->getPost('city_id', 'int');
                    $result['e_objects_addresses'] = Addresses::findByCityId($city_id)->toArray();
                    $emergency_objects->where('o.city_id = :city_id:', ['city_id' => $city_id]);
                    break;
                case 'getEmergencyObjects':
                    $address_id = $this->request->getPost('address_id');
                    $emergency_objects->where('o.address_id = :address_id:', ['address_id' => $address_id]);
                    break;
            }
            $emergency_objects->getQuery()->execute()->toArray();
            $result['emergency_objects'] = $emergency_objects;
            echo json_encode($result, JSON_NUMERIC_CHECK);
        }

Last one returns PHQB object, w/o applied $emergency_objects->getQuery()->execute()->toArray();

Anyone know whats the problem?