BEKASI, Indonesia >> His last words were: “I’m not a thief.”

But the mob, believing he had stolen an amplifier from a mosque, refused to accept the denial. They beat him to death and burned his body as onlookers filmed the proceeding. A triumphant cry went up as he burst into flames.

The lynching this month of Muhammad al-Zahra, 30, in Bekasi, a gritty, industrial suburb of Jakarta, has shocked Indonesia and opened a broader discussion about why vigilante mobs continue to torture and execute petty criminals in the country.

Last month, in Surabaya, a large city in East Java, two young men accused of stealing were beaten by a huge crowd and struck with stones before being rescued by the police. That same month, a video surfaced of residents tying up, interrogating, beating and burning a man on suspicion of stealing in Madura, an island off East Java; the man survived. In June, a theft suspect in Madura was tied to a tree and fatally beaten by villagers.

“Vigilante justice, like the case that just happened in Bekasi, happens so frequently,” said Alghiffari Aqsa, a staff lawyer at the Legal Aid Institute, a nonprofit organization based in Jakarta. “It reflects a lack of trust toward legal institutions. The police are seen as insufficiently responsive,” so villagers take matters into their own hands.

Nearly two decades after Indonesia began its transition to democracy, its judicial system remains weak, plagued by corruption and inefficiency. Despite a significant expansion of police ranks during the last decade, the police are widely considered ineffective at solving everyday illegality.

Frustration with high crime and a lack of punishment for lynch mobs have encouraged more vigilantism.

Mob attacks increased 25 percent between 2007 and 2014, according to the National Violence Monitoring System, a World Bank program that records vigilante killings in Indonesia.

From 2005 to 2014, there were 33,627 victims of vigilante violence in Indonesia, 1,659 of whom died, the program found. Even that figure most likely underestimates the scale of the issue, as the program only monitors violence in half of Indonesia’s provinces.

“The legal system is seen by many people as too lenient for petty theft,” said Sana Jaffrey, a doctoral researcher at the University of Chicago who ran the World Bank program for five years.

For many poorer residents, she said, the loss of a motorbike, or even something as minor as chickens, could greatly damage their livelihood. When convicted thieves are released from jail after just a few months, as is common, it creates a perception that the legal code is too lenient, she said.

Nonetheless, the killing in Bekasi struck a particular chord, in part because Zahra made his living selling electronic equipment, so the amplifier he was accused of stealing may have been acquired legally.

Celebrity preachers swarmed Zahra’s rented home to meet with his widow, Siti Zubaidah, 25, and denounced lynching as un-Islamic. Indonesia’s vice president, Jusuf Kalla, a multimillionaire, dispatched a representative to visit Siti, who is six months pregnant, to pledge financial support.

An Islamic center promised to donate around $19,000 so she could buy a house. And ordinary citizens from Jakarta delivered food and money to the family.

Last week, Bonny Siddarta, 36, who works at a dog shelter in Jakarta, made a long trip from the city to visit the family and donate $900 that he had raised online. He said he was shocked by the killing.

“They judged him so speedily,” he said. “‘This one must die. This one insulted Islam.’”

Siddarta said he hoped the case would be a turning point for Indonesia, but worried that it would not be.

“There are so many cases where the masses take the law into their own hands,” he said.

This time, the police acted swiftly, arresting a pair of men accused of being ringleaders of the mob and pledging to investigate further. Those men did not even know what Zahra was accused of, a police official said.

“They thought he was a motorbike thief,” the official, Rizal Marito, told the news website Tempo. “They didn’t know it was just an amplifier.”

Marito said that residents were frustrated because motorbikes kept being stolen.

Urbanization and an influx of migrant workers have also contributed to the prevalence of lynchings, experts said.

Jaffrey, of the University of Chicago, said that lynching tended to happen in industrial towns like Bekasi that had developed rapidly and swelled with migrant workers.

“The mode of life has changed,” she said. “The pace of life has changed.

“Now more strangers are passing through these areas, and often the residents don’t know what their purpose is,” she continued. “If there is indication of a crime, it can lead to a lynching.”

In Bekasi alone, 29 people have died at the hands of a mob since 2005.

In the poor, tight-knit neighborhood where Zahra lived, residents were furious over the killing of a beloved neighbor.

A poster hung from the house next to Zahra’s with slogans like, “This is a nation of laws, bro” and “Stop vigilante justice.” It bore hundreds of signatures.

Siti, Zahra’s wife, in a gray gown and red head scarf, said she was still in shock. She said she had not had a chance to consider how her children were going to fare without their father.

All she knew was that the mob had committed a great evil.

“Let’s not have there be any future victims of vigilante justice,” Siti said. “If this keeps up, how can we be considered a nation of laws?”

Even Rojali Babelan, the caretaker of the small mosque who accused Zahra of stealing the amplifier, says he has regrets about the killing.

Rojali, in an interview, recounted his version of events that day. Not many visitors come to the isolated mosque, he said, so he took note when Zahra stopped by, ostensibly to pray. After Zahra left, Rojali quickly realized that the amplifier was gone, and, suspecting Zahra, chased him down by motorbike.

Rojali eventually found Zahra at a market in a bustling part of the city. Zahra, shocked to realize that he had been followed, dropped a bag with the amplifier and ran off, Rojali said. “It was definitely my amplifier,” the caretaker said.

When people asked Rojali what the commotion was about, he said that Zahra was a thief. A cry went up, and Zahra was captured and beaten to death.

“I really didn’t agree with that punishment,” Rojali said. “The community should have let the police handle things.”