Resolving encounter cards always places sleeping Vampires. Elder Vampire are Vampires, so they follow the basic Vampire rules unless there is a specific exception for them.
If on the other hand is happening because of the awakening you place him awake as any other vampire.
Cheval31 gives you the right result, but to be absolutely precise, encounter cards always place sleeping Vampires. Here are the steps of the Awakening, page 21.
Follow these steps in order at the end of round 6:
• Resolve Encounter Cards for all Unexplored Rooms. Ignore all Terror Events generated by these Encounter Cards.
• Wake all Vampires. Stand all Vampire miniatures upright.
• Open all the normal Doors.
• Flip all the Vampire ID Cards from the Day side to the Night side, revealing their nighttime statistics and special powers.