Complex sentence: The Foundation became the custodian of the police and evidence files associated with the assassination, including the rifle and fatal bullet, which are on display in a 12,800 sq. foot exhibit in the building.
Split into simpler sentences: The Foundation became the custodian of the police and evidence files associated with the assassination, including the rifle and fatal bullet. The latter are on display in a 12,800 sq. foot exhibit in the building.