The charges included two counts of killing a federal employee and one count of trying to assassinate a member of Congress as well as two additional counts of trying to kill federal workers.
Prosecutors also said investigators found allegedly incriminating evidence at Loughner's residence that indicated that he his actions were premeditated.
From the AP:
Investigators say they seized evidence suggesting Loughner planned ahead.
Investigators said they carried out a search warrant at the suspect's home and seized an envelope from a safe with messages such as "I planned ahead,"' "My assassination" and the name "Giffords" next to what appears to be the man's signature.
A federal prosecutor said Loughner didn't have a lawyer but that an attempt was being made to secure one for him.
According to a press release from the U.S. Attorney in Arizona, Loughner is scheduled to make his first court appearance at 5 pm Monday EST.