This week, we're looking back at the Saint Francis shooting, one year later.

News On 6's Lori Fullbright sat down with the commander of Tulsa's Operations team, who has been studying active shooter cases for 20 years and uses what he learns to teach both police officers and citizens.

He said, first and foremost for police, this was a terrible tragedy with the murder of four, innocent and remarkable people.

Beyond that, there are lessons to be learned from a tactical perspective, for both officers who respond to active shooters in the future and for citizens who might be in a similar situation one day.