FORT HOOD, Texas — Several hundred people gathered at a base stadium where the Army's chief chaplain offered prayers for families and victims of the shooting rampage that left 13 dead and 30 wounded at Fort Hood, Texas.

Chaplain Douglas Carver told those at the Friday vigil — many dressed in fatigues and black berets — to "remember to keep breathing ... keep going."

"God Bless America" and "Amazing Grace" were sung as husbands wrapped their arms around their wives, babies cried and old men in wheelchairs bowed their heads.

It was the first community gathering since the killings.

In Washington, President Barack Obama said the entire nation is grieving for those slain at Fort Hood, and he urged people not to jump to conclusions while law enforcement officers investigate the shootings.

Obama met Friday with FBI Director Robert Mueller and other federal leaders to get an update on what they've learned. "What we do know is that there are families, friends and an entire nation grieving right now for the valiant men and women who came under attack yesterday," the president said.

His aides, meanwhile, worked to make way for Obama to attend a still unscheduled memorial service for those slain at the nation's largest military post. The White House's top spokesman said Obama would attend that service and emphasized it would take place at the family's convenience, and that it will not be dictated by the president's schedule.

Later the president spent nearly two hours visiting wounded soldiers at Walter Reed Army Medical Center. The president met with 19 soldiers being treated at Walter Reed, as well as the families of three soldiers in intensive care, and hospital staff. He also awarded two Purple Hearts.