There were a few different things that were needed in the crime lab. Normally, he'd let someone else handle it but this was his job. This was where he was needed. The Captain and Joe both counted on him. So he doesn't expect anyone else to end up in the lab, nor does he even notice at first. Not until he gets that feeling anyway. Like he needed to look. That someone was there.

"I'm sorry, but you can't be..." He starts before looking up and feeling like he couldn't breathe. This was NOT possible. It couldn't be possible. He felt like someone had just punched him in the chest and ripped out his heart. She couldn't be there.