Breaking News from CBS

• How tornado warning systems work

  Despite advanced technology, Moore, Oklahoma's tornado warning system still relies on someone pulling a lever to activate the alarm

• Video: Mother and daughter share stories of survival

  Courtney Brown and her second-grade class took shelter in a hallway at their school; Courtney's mom rushed to what was left of the school to search for her children. The mother and daughter tell Norah O'Donnell their story.

• Oklahoma native's home destroyed for the second time

  Nancy Davis, 94, helped save lives during the tornado by sharing her shelter, built after the historic 1999 twister in Moore

• Video: Oklahoma National Guardsmen comb through rubble

  Oklahoma National Guardsmen are scanning splintered neighborhoods for any spaces big enough to shield survivors. Scott Pelley joined one of the teams during their search-and-rescue efforts.

• Okla. family mourns child killed at school following tornado

  Joshua Hornsby raced to find his 9-year-old daughter at school when the tornado hit; he got there 10 minutes too late