Howard Carter, the English archaeologist of some repute, entered King Tut's sealed tomb before any one else had for many thousands of years. He had access before any other expeditions arrived. His own notes and photographs suggest that much of the treasure was in tact when he first discovered the tomb, but disappeared soon afterward.
Yes, Howard Carter was likely the person that robbed the tomb prior to its 1922 opening, because Howard Carter was the only person with the knowledge, skills, and interests to find the tomb and rob it. Carter was feverishly searching for and working on finding the tomb up until that point, and was the person who would have had an interest in robbing it. It was probably him because he was the only person capable of doing so.