Samuel Granillo was a 17-year-old junior at Columbine High School when two gunmen walked the halls committing one of the worst mass shootings in recent US history.

He survived by hiding in the cafeteria kitchen for three hours until help arrived - but good friends were lost.

Memories and nightmares of that day are ever present in Mr Granillo's mind, but now at 30 he has built a life for himself as a filmmaker.

He is even working on a documentary called "Columbine: Wounded Minds" advocating counselling for other Columbine survivors.

But now he must live through the tragedy of another mass shooting - this time at an Aurora, Colorado, movie theatre where one of his friends was killed as he watched the new Batman film.

Mr Granillo tries to draw on experiences from Columbine to help surviving friends, but he must balance this with the rush of memories the killings bring back.

Produced by the BBC's David Botti

Additional photos: Getty Images, AFP, and courtesy Samuel Granillo