Who is this lady?

[RJNorton]

In Manhunt it says:

"The room was empty of all visitors now, save one. Edwin Stanton and the president were alone. The morning light streaming through the back windows raked across Lincoln’s still face. Stanton closed the blinds and approached the president’s body. He took from his pocket a small knife or pair of scissors and bent over Lincoln’s head. Gently he cut a generous lock of hair—more than one hundred strands—and sealed it in a plain, white envelope."

Stanton left no statement about doing this that I know of. So how are these details known (given Stanton is alone)? I really wonder why Stanton might have had a pair of scissors in his pocket. Ouch. Whoever wrote this (i.e. Mr. Swanson's source) apparently didn't know how Stanton might have clipped the lock of hair, but the person somehow did know "the morning light streaming through the back windows raked across Lincoln’s still face." Pretty strange, IMO.