Updated: 6:05 p.m.

Speaker John Boehner (R-Ohio) on Sunday morning denounced the attack on Rep. Gabrielle Giffords (D-Ariz.) that left six dead and 14 others wounded, including Giffords.

“An attack on one who serves is an attack on all who serve,” Boehner said in brief remarks from West Chester, Ohio. Flags on the House side of the Capitol will be flown at half-staff in honor of Gabe Zimmerman, a 30-year-old Giffords aide who died in the attack.

Boehner also said he has informed the FBI that “the House stands ready to assist in any way possible” in the investigation.

While the attack is a reminder that “service to our fellow citizens comes with a risk … this inhuman act should not and will not deter us from our calling to represent our constituents and to fulfill our oaths of office,” Boehner said.

“No act, no matter how heinous, must be allowed to stop us from our duty,” he added.