In this Thursday, May 19, 2016 photo, a framed photo of Mandy Pifer and her boyfriend, Shannon Johnson, is placed next to her bed in Los Angeles. Nearly six months ago, Johnson was one of the 14 people killed in the San Bernardino terrorist attack.

In this Thursday, May 19, 2016 photo, a framed photo of Mandy Pifer and her boyfriend, Shannon Johnson, is placed next to her bed in Los Angeles. Nearly six months ago, Johnson was one of the 14 people killed in the San Bernardino terrorist attack. / The Associated Press

It’s been a year and a half since a deadly mass shooting in San Bernardino, California. The two attackers were killed after they gunned down 14 people. Georgia native Shannon Johnson, a graduate of Macon’s Windsor Academy, was one of them. He died shielding a co-worker in the attack. Friends of the family say Johnson’s heroics were also in his DNA. His father died years earlier trying to save a co-worker during a factory accident. We talked with Shannon’s brother, Rob, about the family’s heroic legacy.Rob Johnson shares his family's story of sacrifice.

So, what exactly makes a hero? Do genetics really play a role? We talked with professor Zeno Franco of the Medical College of Wisconsin. 

Zeno Franco of the Medical College of Wisconsin explains the psychology of heroic behavior.

https://www.youtube.com/watch?v=-kcRDoo1sh4

Tags: Shannon Johnson  Rob Johnson  Zeno Franco  psychology  Atlanta  Georgia