From this article:
He is known to be German, and has been described by police as white, 6ft tall, of a slim build and with short blond hair. <snip>
Two blond-haired men were seen on the balcony of an empty apartment two doors from the McCanns’s apartment at 2.30pm on the day of the disappearance. Blond men were again seen near the apartment at 4pm, 6pm, and 11pm.
The suspect was in the Praia de Luz area on May 3, 2007, and is known to have received a phone call at 7.32pm, which lasted 30 minutes.
Madeleine was reported missing from the resort at 10.14pm on
The Mccanns had routinely left their 3 children in the apartment the previous 5 nights , so someone observing this could seize the opportunity to enter the apartment. If these men were on a balcony nearby they could have been watching anyday , and knew an adult free apartment would be there later .