Ji Zhongxing, 34, was being prevented by police from handing out leaflets at the airport which described the desperate story of his life.
Witnesses said that Ji then shouted out: "I have a bomb, stay away from me!" And then he set off the device.
He blew off his own hand and slightly injured one policeman.  Witness accounts immediately appeared on social media. The mayhem after the blast was described by East Asia analyst Stephanie Kleine-Ahlbrandt on Twitter who was there at the time: "Huge explosion followed by panic, smoke and dust at Terminal 3."
On Tuesday 15 October Ji was sentenced to six years in prison for his act.
His actions were condemned as reckless and the court said that he had to be held accountable, but Ji Zhongxing has nonetheless attracted a great deal of sympathy and   struck a chord with China's legions of microbloggers.
One user posted: "The court believes that he must take legal responsibility for his action. But who should take legal responsibility for what had driven Ji Zhongxing to do all this?"
If the world has now forgotten about what drove him to detonate the bomb on 20 July, China's blogging public has not.
His story is seen as typical of China's most marginalised and unfortunate members of society; petitioners driven to desperate measures when faced by an apparently unyielding bureaucracy.
Petitioners are people who believe they have been wronged  by lower levels of government and bring their grievances to the attention of the higher authorities.
Although they are officially allowed to do this, rights groups say the government does prevent petitioners speaking out about their treatment and allege there is an entire underground system of surveillance and so-called "black jails" used to silence them - the authorities routinely deny such allegations.
But what is clear is that Ji Zhongxing had been campaigning for years  to have his story heard - to little avail.  It all centres around one incident on 28 June 2005 and there are two versions of what really happened that night.
At that time Ji had a day job as a security guard for a firm in  Dongguan in south China's Guangdong province.  By night he drove an auto-rickshaw to ferry passengers around to supplement his income. He wanted to save money to marry his girlfriend - who was also a migrant worker in the city.
In the early hours of that morning members of a local security force, known as zhianduiyuan, employed by the government to maintain order,  approached Ji who was driving his rickshaw and demanded to check his documents.
Their job included tackling unlicenced vehicles such as his.
Ji says that he was chased by the officials and once he was caught he received a brutal and sustained beating that left him paralysed in his lower limbs. The officials say he was injured after he fell from his vehicle.
On his microblog (which has now apparently been deleted) he said: "seven or eight zhianduiyuan blocked the road - iron bars in their hands. As I was about to stop, one of them launched an assault to my face with his iron bar. As a result, me and my passenger Gong Tao were thrown to the ground."
Ji said that he lost consciousness after a single blow. When he woke up, he found himself in a hospital and the passenger who had been in his rickshaw at the time told him that the local officials had continued beating him on his legs and waist even after he fell.  By the time police had appeared, he was unconscious.
Like many of the migrant workers in Dongguan, Ji had no insurance and no relatives to rely on.  His girlfriend, a migrant worker herself, looked after him in hospital for seven days. After she learned that Ji was paralysed from the waist down, she left him, his family say.
He was left to survive on his own and so began his quest for redress.
Ji became one of China's estimated hundreds of thousands of petitioners.  There are no official figures but rights groups say the problem is visible in China's major cities - they can be seen standing in front of government offices waiting their turn to be seen.
The case did make it to the courts in Dongguan but it ruled against him.  He posted gruesome pictures taken of his injuries after the incident but it failed to convince the authorities. An appeal also failed.  In the end, the case was only dealt with as a traffic accident.
He then went to Beijing to launch petitions and to seek justice for the alleged attack. He met with little success. After years of repeated attempts to seek compensation from the higher authorities , Ji ended up in Beijing airport on 20 July with a home-made explosive device.
His elder brother, Ji Zhongji, told the BBC that Ji had originally gone to Dongguan to seek his fortune.  He would have joined countless others in making that journey at the turn of this century.
Dongguan, a city famous for entrepreneurship, is just two hours by train from Hong Kong.  Hundreds of thousands of people, mostly from poor rural areas, are attracted to the city hoping for a better life. The city has approximately five million migrant workers - that is four-fifths of its population.
Ji himself was born in a village near the city of Heze in Shandong province, almost 1,800km (1,118 miles) away. His brother said that Ji stopped going to school when he was at primary because "our family was very poor".
Heze is a medium-sized and nondescript city by Chinese standards, with a population of about nine million and surrounded by a vast agricultural belt which is known for its grain, cotton, forestry and livestock.
The brothers' father was a farmer. Their mother died 12 years ago, around the time Ji left for Dongguan.
"My brother believed that life could be improved through hard and honest work, and that was exactly what he did in Dongguan," Ji Zhongji said.
He recalled going to visit his younger brother in hospital after his girlfriend left him. When he brought him back to Heze, he had come full circle having apparently achieved nothing.
"We didn't have enough money for the train fare and had to beg the train operators for compassion," Ji Zhongji said.
He said that Ji Zhongxing had fervently hoped the law would support him.
Ji then lived with his father at home, only making the occasional journey to Beijing as a petitioner.
"My brother is very sad. He is angry with the way the government, the police and the court dealt with his case," said Ji Zhongji.
"My father told me that he disappeared one day, very unusual considering his paralysis. And he phoned my father saying he was going to Beijing," his brother said.
It is not known how Ji Zhongxing managed to pass security checks and enter the airport with an explosive device.
"My brother didn't want to hurt anyone. He just wanted to air his grievance. He gave off a warning before the explosion," Ji Zhongji said.
In court Ji said he regretted his actions but the judge decided he had to be held responsible and sentenced him accordingly. His brother says they will appeal.
Analysts say any appeal is unlikely to be successful, but Ji has made his story known and many microbloggers have taken this tale to heart.
When a man in a wheelchair detonated a small home-made bomb in Beijing's international airport in July, he momentarily captured the world's attention.