The man who is said to be behind the Shanghai Airport explosion, which injured four people on Sunday, was allegedly deep in gambling debts.

According to police investigators, the man who had been identified as Zhou Xingbo, threatened to do something "totally crazy" before setting off an improvised bomb made from firecrackers inside the airport's terminal, reported the New York Times.

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The injured bystanders were hit by shards of glass, while the suspect tried to kill himself by slashing his throat with a knife after setting off the bomb.

He survived but is now in critical condition.

The statement from the Shanghai Police was the first account to shed led light on the possible motives behind the Shanghai Airport explosion.

It however categorically ruled out that Zhou was harboring broader political grievances, but instead revealed that his act of violence was the result of being mired in debt.

Investigators have learned that, Zhou, a 29-year-old migrant worker from Guizhou Province in southwest China, was employed by an electronics factory in the industrial district of Kunshan.

While working at the plant, Mr. Zhou "indulged in online gambling and lost all his savings," disclosed the police report. "He regularly borrowed from friends to get by."

Before carrying out the attack, Zhou sent a message via WeChat, a highly-popular mobile messaging service in China, saying "I owe a lot of money to a lot of people."

Authorities found remnants of firecrackers in Zhou's rented room in Kunshan.

He added: "Getting ready to do something totally crazy, sure to lose little life." apparently referring to his own life.

Zhou boarded a bus to Shanghai on Sunday morning and proceeded to the airport in the afternoon.

It was there where he detonated at least one beer bottle packed with powder from firecrackers, sending terrified passengers scampering for safety.

The police report was unclear through how many homemade bombs Zhou detonated, which reportedly caused the explosion at the Shanghai Airport.

TagsShanghai, Shanghai airport, Shanghai Airport Explosion