From Inside the Grey House:
Vincent watched as Jesse did as he ordered. The vampire thought that with Natalia distracting the Slayer, Jesse could tackle Dean. He watched as Jesse ran, heard Natalia’s warning and watched as the Slayer turned slowly, lifted his sword and beheaded Jesse with the sword he held lightly in his hand. It was a large sword, but the way the Slayer was holding it, it was obviously very light. Too late he noticed these things as Jesse turned to dust. His eyes grew wide. Jesse had fed; they had all fed, before coming here tonight. He didn’t know how old Jesse was, but had known the shy vampire for over one hundred years. A beheading would not kill him.