Why did Watcher Rorschach die?

Because Rorschach wants to tell the world the truth that others framed dr. manhattan, but this truth can't be said. Rorschach's real name is Walter kovac. He has never been warm by his family since he was a child, and he is often bullied by others, which leads to his violent tendency in the future. When he grows up, he works in a clothing factory.

At the end of the movie Watcher, Rorschach sacrificed millions of people because he didn't agree with Pharaoh's way of making the world a beautiful utopia. He didn't compromise, but was killed by dr. manhattan voluntarily.

The fourth chapter of Watcher mentioned that Rorschach's mask was modified from a skirt made by dr. manhattan. Rorschach worked as a worker in a clothing factory, 16 years old.

At the age of 22, he made a skirt for Katie genovese with this special fabric invented by dr. manhattan. The viscous fluid in the middle of the double-layer fabric is sensitive to heat and pressure. But Katie genovese wouldn't accept it because she was ugly. Rorschach thinks this cloth is beautiful. Two years later, Katie was killed, and Rorschach made this mask for herself with that cloth.