ronald anderson , 48 , was arrested and charged for the crime spree .
anderson was previously convicted of manslaughter and arrested in an assault case involving his ` visibly afraid ' girlfriend .
the kidnapped woman was found safe - she may be related to suspect .
the guard , lawrence buckner , died at a hospital in cheverly , maryland .
officer and suspect both conscious when they were taken for medical care .
guard saw two people fighting in a car that matched the description of a vehicle described in a report of an armed kidnapping .
incident took place at gate of u.s. census bureau in suitland , maryland .