The Death of Edward. B

You found the real murderer. Sam"the witch".A wrote that letter to Edward because he was the one to let the dog chew up her stuff and destroy her favorite book hence the "W" on the letter. She said she was in Small Animal Management and saw Edward upstairs but how could she when the stairs and elevators were blocked and turned off. She threw the electric pencil sharpener at him but did not mean to kill him just injure him a bit.
Great job detective.