Joel Pollak, the editor-in-chief of Breibart.com, described his friend and boss as "an extemely kind man and a great friend."
"Andrew would stand up for anybody - left or right. He had friends on both sides. As long as they were willing to play by the same rules, state their biases and respect diversity of opinion," Pollak told ABC News. "He really believed passionately in fairness, and what really made him special was his willingness to fight for it."
Conservative leaders are also expressing the loss of Breitbart in the community.
After giving a speech in Dalton, Ga. this morning, Rick Santorum was asked about Breitbart's death, which had been announced during his speech.
"Obviously prayers go to him and his family and it's a big shock. What a powerful voice," Santorum said. "What a huge loss, in my opinion, for our country and certainly for the conservative movement and the prayers go out to my family. I'm sorry to hear it."
Citizens United President David N. Bossie, issued a statement on Breitbart's passing "with a heavy heart," in which he said, "Andrew was a trailblazer and icon when it came to internet based media. He was truly a one of a kind transformational figure and warrior in the conservative movement and he will be sorely missed."