LITTLETON - It's been 14 years since a day that changed Karissa Marcum's life forever.

Saturday marks the 14th anniversary since the Columbine High School shooting massacre on April 20, 1999.

"In some ways it feels like it just happened. I can go back there in my mind and be hiding under that table and hear those 'pop, pop, pop, pop' right now. But sometimes it feels so far away. It was a whole other era. It was when I was a child," Marcum said.

Now at 28 years old, Marcum spends her time not thinking about that day, but making every day since count.

"I decided at 14 years old, I was going to live my life to the fullest and carry them with me," Marcum said.

Since Columbine, there have been several other mass casualties including Virginia Tech, Newtown, the Aurora theater shooting and now the Boston Marathon.

Marcum is telling her story in hopes it helps others affected by those events, move forward.

"You can choose how you are going to live you or life and the attitude you are going to have in spite of your circumstances. I think that has been important to help me heal and move on," Marcum said.

She also talks about leaning into her community and her faith that have been a big parts of the healing process.

And now her message is simple: do good.

"There is so much evil and we all feel out of control. I think we also see what we saw at Columbine, Aurora and now Boston and there are a lot of good that come out of these. The people that choose to do those bad things are in the minority, but there are people that are choosing good every day and that ultimately is more powerful than the bad decision that those people make," Marcum said.

She hopes tragic events like what's going on in Boston, pulls all of our communities closer and creates a chain reaction for people to try to do good and pay it forward.

"Hope exists if we can come along side people. I don't know if that's going to prevent the next school shooting or next bombing but I know it couldn't hurt," Marcum said.