Using AWS in Codeigniter - CI_Ec2Client class not found

I am trying to implement the Amazon Web Service Feed we are using into my Codeigniter project through the controller.I can do it through the view fine, but when I try it through the controller I get the following error

Non-existent class: CI_Ec2Client

I have changed the class name from Ec2Client to CI_Ec2Client but no luck. The SDK is located in system/libraries/aws

My controller code is as follows:

require 'aws/aws-autoloader.php';
$this->load->library('aws/Aws/Ec2/Ec2Client');

$ec2Client = Ec2Client::factory(array(
    'key'    => 'KEY_HERE',
    'secret' => 'SECRET_HERE',
    'region' => 'us-west-2'
));
$result = $ec2Client->describeInstances(array(
    'MaxResults' => '1000'
));

This throws the error. However my view code is pretty much similar and it works fine.

require 'aws/aws-autoloader.php'; 
use Aws\Ec2\Ec2Client;
$ec2Client = Ec2Client::factory(array(
    'key'    => 'KEY_HERE',
    'secret' => 'SECRET_HERE',
    'region' => 'us-west-2'
));
$result = $ec2Client->describeInstances(array(
    'MaxResults' => '1000'
));

The reason I am trying to load it through my controller is so I can call it every few minutes through an ajax call.

Any idea what I am doing wrong? Can't seem to figure it out!