Nasim Aghdam felt that she was not getting her due from YouTube. For eight years, the 39-year-old posted hundreds of YouTube videos, garnering roughly 30,000 subscribers and more than 9 million views. She was a small part of YouTube’s success story — the army of independent creators who catapulted it to the top of the video heap. And then on Tuesday, Aghdam entered YouTube’s San Bruno headquarters with a gun, injuring three employees and killing herself.