Sinaga typically approached his victims in the street. The rapist operated in a small area surrounding his flat. His targets were men mostly in their late teens or early 20s who had been out drinking, often in the nearby nightclubs.
Some were on their way home, others had become separated from friends.
Many were too drunk to remember their conversation with Sinaga, but for those who did there was no indication of a sexual motive. Sinaga used various pretexts to entice each to his flat.
Some victims could recall being provided with a drink and then blacking out.