For eight years, motorcycle taxi driver Ji Zhongxing sought justice for what he said was a beating by city guards that left him paralyzed. It was his frustration, his brother said, that led Ji to push his wheelchair through a crowded terminal at Beijing's main airport and detonate a homemade bomb.
Ji injured no one but himself, but Saturday's incident has raised questions in China about whether the country can adequately address the grievances of increasingly marginalized members of its society and cast a spotlight on the failures of the country's legal system to provide a sense of fairness.
Ji, 33, from the eastern city of Heze, had been petitioning Chinese authorities for years after the 2005 attack, which left him paralyzed from the waist down and more than $16,000 in debt, his elder brother Ji Zhongji said.
"They beat him up for no reason. My brother was wronged," Ji Zhongji said by phone Monday. "If even one person had stood up and said a word of fairness to my brother about his case, he would not possibly have ended up where he is today." (Read more: Beijing airport bomber was almost beaten to death)
In an era of burgeoning gaps in income and social status, China's courts - controlled by the Communist Party's local political and legal affairs committees - are widely perceived as being corrupt or more likely to protect the interests of local officials than exercise justice.
People like Ji, migrant workers with little education and zero political connections, make up Chinese society's lowest rung. When the legal system fails them, they turn to petitioning - a centuries-old system of sending appeals to government officials in Beijing in the hope of gaining redress.
In this photo released by China's Xinhua News Agency, medical workers and policemen attend to injured Ji Zhongxing at Terminal 3 of Beijing International Airport in Beijing. (AP Photo/Xinhua)
But those appeals rarely work and frustration among petitioners can mount and boil over into violence. In the prosperous port city of Xiamen in June, authorities have blamed a fire on a bus that killed 47 people on a disgruntled man named Chen Shuizong who apparently was destitute and had been pleading with local officials for eligibility for social security payments.
While condemning such attacks as a new kind of "terrorism," a commentary by the Xinhua Daily Telegraph, a newspaper published by the official Xinhua News Agency, also urged that a higher priority be made of ensuring that people feel they are treated justly. (Read more: Beijing airport blast sparks concerns over way of protests)
"Every person who feels like they have been wronged could be a time bomb," the commentary said.
Ji apparently started a blog in 2006 to seek public support for his cause, writing in a final post that year: "We pleaded to the heavens but the heavens would not respond. We called out to the earth and the earth was silent."
The elder Ji said his brother had been driving a motorcycle taxi in the southern city of Dongguan when he was allegedly beaten up by security guards in a 2005 attack. Ji Zhongji, who is working in Inner Mongolia, said he did not know what led to his brother's action on Saturday, but that he knew that his brother had been frustrated by his efforts to find justice.
After Saturday's blast, Ji was sent to hospital where he underwent surgery to amputate his left arm, state media have reported. His status was not immediately clear. Beijing police did not respond to a faxed list of questions. The Dongguan city government said an investigation had been re-opened into Ji's case though it defended the authorities' handling of his petitions. It confirmed in a posting on its official microblog account that Ji had been seeking about 330,000 yuan ($50,000) in compensation for medical bills and wages lost from not being able to work.
Liu Xiaoyuan, a rights attorney who has tried to seek justice on behalf of many petitioners, said Ji's case showed how ineffective the system is in helping people with grievances. Petitioners are a symbol of China's failure to build a justice system that ordinary citizens consider fair, he said.
"This case reflects what happens if the system does not provide ways for petitioners to be treated reasonably," Liu said by phone. "Sometimes it will force them to take up extreme measures, because they think that unless they do that, no one will listen."
Petitioners are often met with violence when they attempt to take their cases to Beijing, with local governments sending "interceptors" to stop them - with force - and keep them in informal "black jails" until they can be sent home. (Read more: Sympathy for China airport blast protestor)
The case takes place as China's new leadership has called on the judicial system to provide fairness for all. Social commentators have cited Saturday's blast as a reason for the authorities to examine inequalities in the system and the apathy with which the poor are often treated.
Shi Shusi, a commentator for the Workers' Daily newspaper, wrote: "In some areas, citizens' legitimate demands are being ignored and public power rides above the law. ... This completely blocks the ability of people at the lowest levels to defend their rights."
Citing the "black sound of the explosion," Shi asked, "For whom has the alarm sounded?"