The original version of the Hulk was often shown as simple and quick to anger. His first transformations were triggered by sundown, and he would change back to being Banner by dawn. Hulk evolved over time into a troubled soul with a significant back-story whose transformations were triggered by emotional stress. When Peter David began writing the series in May 1987, his stories showed that Banner had serious mental problems long before he became the Hulk. And he revamped the personality significantly: The Grey Hulk became a Las Vegas mob enforcer named Mr. Fixit, a shadowy behind-the-scenes figure.