Shanghaiist's James Griffiths is reporting that the man, Ji Zhongxing, had been attempting to give out leaflets in front of the airport, but was prevented from doing so. He then began yelling, drawing crowds and security, and detonated the bomb shortly after.
According to a blogpost the bomber apparently wrote on Sina Weibo, Zhongxing was left disabled after police used a steel tube to beat him in 2006, possibly because he had been running an illegal tuk-tuk (taxi) service.
After he was prevented from distributing leaflets, Zhongxing allegedly began warning people to keep their distance because he was going to "blow himself up," but "no one believed him." Zhongxing apparently waited until police had arrived before detonating the bomb outside the arrivals exit of the airport's Terminal 3. Engadget Chinese's editor-in-chief Richard Lai reported on Twitter that police said Zhongxing had used gunpowder to make the bomb.
Zhongxing is now in the hospital being treated for his injuries. According to Shanghaiist, the bomber fractured his left arm and did not "seem to have intended to hurt anyone else."