Chen Shuizong (59), a native of Xiamen city, allegedly set ablaze the bus to "vent personal grievances", state-run Xinhua news agency reported.
Chen was identified as the arsonist of the fire, the information office of the city government said in a statement.
The statement said that an investigation and DNA evidence found that Chen was the suspect.
Xiamen police found a note in the suspect's house, which revealed that Chen was "unhappy and pessimistic about his life", and planned the arson to vent personal grievances.
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All this suggest it is a arson attack and serious criminal case, an official said adding that the man was identified with the help of survivors who reported that they smelt gasoline followed by an explosion.
In cases like this Chinese officials release few details about those who indulged in such acts to prevent copycat attacks.
Other than his name and year of birth, no details were provided nor the content of his letter was made public.