WINNETKA --Twenty years ago Tuesday, lives changed forever when Laurie Dann walked into a elementary school on Chicago's North Shore and opened fire.By the time her shooting spree was over, one child was dead and five others were wounded. A college student was also shot before Dann turned the gun on herself. The second-graders who were in that class at Hubbard Woods School are today pushing 30 years of age - some with families of their own. Most don't care to talk about what happened back then, certainly not on the day of reminder. But after an event so unexpected the thought almost immediately 20 years ago was about "innocence shattered." "It's hard to fathom the impact it had. It was terrible," said Herb Timm, Retired Winnetka Police Chief. There were no locks on school doors back then. Checking in at the principal's office was a courtesy more than anything else. So no one expected that a mentally disturbed woman would walk into a classroom at Hubbard Woods School and start shooting second graders. Nicky Corwin died. "My neighbor said there'd been a shooting at the school. My heart clenched and my stomach dropped. And 20 years later, whenever I see another new story about another school shooting, I feel the same way," said Marcia Adelman, Illinois Council Against Handgun Violence. Adelman's son was a second grader at Hubbard Woods the day of the shooting. He was not harmed. She and others impacted by the shooting have spent the last two decades working for gun control. Phillip Andrew, who was shot by Dann just before she took her life, went on to become an FBI agent. "Recognizing the need to I.D. mentally ill people and pay attention was a big issue," said Timm. Amidst the anger and pain that followed the shock, a lot was learned. "We didn't really have any model. This was really the first shooting in a school," said Dr Eitan Schwarz, psychiatrist, Northwestern University. Schwarz led a team of mental health professionals in the aftermath of the Dann shooting. They were able to develop a much better understanding of post traumatic stress in children and how trauma victims are often reluctant to seek help. In every subsequent school shooting, Schwarz is called for advice. Police departments now routinely train for what was once unthinkable. Just last week, Chicago's police superintendent said his officers need semi-automatic rifles in part because they would be more accurate and reliable in the event of a school-hostage crisis. And two people whose lives were changed say we're still learning 20 years after Dann. "People should be looking at how can we improve this not, how can we affix blame," said Timm. "This is not an urban problem. It's not just an inner city problem. It's everyone's problem," said Adelman. Winnetka passed a handgun ban after the shooting. A park was named in Nick Corwin's memory. School doors are now kept locked almost everywhere. And the term "crisis counselor" - seldom used 20 years ago - is now familiar.