Updated

WASHINGTON -- President Barack Obama will travel to Tucson, Ariz., on Wednesday to attend a memorial service for the victims of last weekend's shooting rampage.

White House spokesman Nick Shapiro said late Monday that the president would speak at the service, and that first lady Michelle Obama would accompany her husband.

The University of Arizona said the service would take place at 6 p.m. local time on the campus and would be free and open to the public.

Democratic congresswoman Gabrielle Giffords is in critical condition after being shot in the head Saturday. Six others died and more than a dozen were wounded outside a supermarket where Giffords had set up a booth to hear the concerns of constituents.

Obama observed a moment of silence for the victims at the White House on Monday. He said the nation is shocked and grieving.