A federal judge ruled Wednesday that the suspect in the Tucson, Ariz., shooting rampage that wounded U.S. Congresswoman Gabrielle Giffords is "mentally incompetent" to stand trial.

The decision by U.S. District Judge Larry Burns indefinitely delays the trial surrounding Jared Loughner's case. The 21-year-old will now be sent to a federal facility for up to four months in an effort to restore his competency.

Loughner pleaded not guilty to charges stemming from the Jan. 8 assassination attempt against Rep. Giffords that killed six people and injured 12 others.

Wednesday's ruling comes after Loughner spent five weeks in March and April at a federal facility in Missouri, where he was examined by court-appointed mental health professionals.