Updated: 10:27 p.m.

The family of Jared Loughner barricaded themselves inside their Tucson home Monday and refused to allow FBI agents inside to continue an investigation into a deadly Saturday shooting, the Arizona Republic reported.

Loughner, 22, was taken into custody Saturday after an attempted assassination of Rep. Gabrielle Giffords (D-Ariz.) left the lawmaker severely injured and six others dead.

U.S. Magistrate Judge Lawrence Anderson ordered later Monday that Loughner be held without bail, the Arizona Republic reported. Anderson informed the defendant that he could be sentenced to life in prison or the death penalty if convicted of the deaths of U.S. District Judge John Roll and Gabe Zimmerman, a Giffords aide. He could receive up to life in prison if convicted of shooting Giffords and up to 20 years in prison if convicted in the shootings of two other aides to Giffords.

FBI agents attempted to gain access to the house at 12:25 p.m. Mountain time only to discover the family had erected a plywood barricade blocking access to the front porch. The family refused access to the agents, who banged on the barricade, yelling, “This is the FBI. Let us in,” according to the newspaper.

It is unclear why the family would try to block access to the house, which law enforcement officials searched over the weekend. The Arizona Republic reported that FBI agents were eventually able to talk to family members Monday and to go inside.