WP_Query returns more custom types than requested

Hello,
I have a very strange situation running WP_Query in order to display the last ‘event’ records, where ‘event’ is my custom_type. The code is the following:

$args_events = array(
'post_type' => 'event',
'order' =>'DESC',
'orderby'=> 'date',
'showposts' => 15);
$query_events = new WP_Query( $args_events );

The problem is that the query returns not just ‘event’ records, but also other custom types. I’m writing here hoping someone else experienced the same situation.

Running

query_posts(array(
'post_type'=>'event',
'orderby'=>'date',
'showposts'=>15));

I got only events, but sorting by date DESC is not working for unknown reason.

Thank you in advance,