Police officers investigate outside North Park School after a fatal shooting at the elementary school, Monday, April 10, 2017, in San Bernardino, California. (AP Photo/Ringo H.W. Chiu)
Small children are seen walking hand-in-hand as they head to safety after a fatal campus shooting in San Bernardino on Monday, April 10, 2017. (KABC)
Students give high fives to school staff and volunteers after being released following a shooting at a San Bernardino elementary school on Monday, April 10, 2017. (KABC)
Parents rush to meet their children in an emotional reunion following a shooting at a San Bernardino elementary school on Monday, April 10, 2017. (KABC)
School buses are seen near the site of a campus shooting on Monday, April 10, 2017, in San Bernardino, California. (Beatriz Valenzuela/Southern California News Group)
An armed law enforcement official runs across the street on Monday, April 10, 2017, in San Bernardino, California. (Beatriz Valenzuela/Southern California News Group)
A police officer stands guard outside North Park School after a fatal shooting at the elementary school, Monday, April 10, 2017, in San Bernardino, California. (AP Photo/Ringo H.W. Chiu)
Parents and guardians of North Park Elementary School students wait at Cajon High School to pick up their children Monday, April 10, 2017, in San Bernardino, California. (AP Photo/Jae C. Hong)
A police office stands guard outside North Park School after a fatal shooting at the elementary school, Monday, April 10, 2017, in San Bernardino, California. (AP Photo/Ringo H.W. Chiu)
Police officers investigate outside North Park School after a fatal shooting at the elementary school, Monday, April 10, 2017, in San Bernardino, California. (AP Photo/Ringo H.W. Chiu)
Police officers stand guard outside North Park School after a fatal shooting at the elementary school, Monday, April 10, 2017, in San Bernardino, California. (AP Photo/Ringo H.W. Chiu)
Police lined the perimeter of North Park elementary following a shooting inside a classroom. (Photo/Rick Sforza with Southern California News Group)
Firefighters don body armor at North Park Elementary, where a shooting happened Monday, April 10, 2017. (Photo/Rick Sforza with Southern California News Group)
A small group of students and teachers wait at H and North Park following a shooting inside their school. (Photo/Rick Sforza with Southern California News Group)