By Agence France-Presse
Officials had said Friday that the blasts had killed one person and injured another.
The suspect, identified by his surname Guo and part of his first name Tao, first killed another man with whom he had an economic dispute in nearby Songyuan city before driving to Changchun city where he rented an apartment, the city's Chaoyang district public security bureau said in a statement posted on social media.
In an underground garage of the Wanda Plaza in Changchun, Guo blew up his car, police said.
Afterwards, at his 30th-floor apartment, Guo "ignited self-controlled explosive material" and died, police said.
People were evacuated from buildings surrounding the Wanda Plaza building on Friday and social media footage showed people fleeing on the crowded road abutting the Wanda building.
Guo, 56, had cancer and was "profoundly pessimistic", police said, adding follow-up work on the case was continuing.
Violent crime has been on the rise in China as the nation's economy has boomed in recent decades and the gap between rich and poor has widened rapidly.
Studies have also described a rise in the prevalence of mental disorders, some of them linked to stress as the pace of life becomes faster and support systems wither.
Disgruntled Chinese citizens have in the past bombed local government offices and public places to try to draw attention to their grievances.
In November, a driver rammed his car into a group of children crossing a street in front of an elementary school in northeastern Liaoning province, killing five people and injuring at least 19.
The man had been contemplating suicide "due to quarrels" with his spouse before the tragedy occurred, according to a report by official news agency Xinhua.
The incident in Changchun comes just over a week before the Lunar New Year holiday, which Chinese usually welcome with firecrackers and fireworks.