David Cavalieri, 40, then sent e-mails from his girlfriend's account to make it look like she was still alive, Simpson added.
Authorities said Cavalieri called 911 on Wednesday saying he was suffering from self-inflicted stab wounds. When rescue workers checked to see if anyone else was at the condominium on Timber Ridge Terrace, authorities said they found 37-year-old Stacie Lynn Harper's body under the bed.
Cavalieri was charged with first-degree murder after he was released from Inova Fairfax Hospital and is being held without bond.
Simpson said Thursday that it appears the slaying followed an argument over money.