HELONG, China » On a cold, clear winter day last month, a North Korean soldier packed a pistol and slipped across the frozen Tumen River into northeastern China. He trekked about a mile to the tiny village of Jidi Tun. Then at dusk he opened fire on two elderly couples, killing all four people.

That night, a phalanx of Chinese security forces hunted him down and shot him in the stomach. They ferried him to the hospital here in Jilin province, about 20 miles from the scene of the killings, but the soldier died a day or so later and his body was returned to his homeland, according to local accounts.

Most likely hungry from the shortage of food that plagues some units of the armed forces in North Korea, he was looking for sustenance, local officials said; some reports said he was drunk.

In most places, a solitary killer from another country would not cause much anxiety. But in China, whose relationship with North Korea has gone from warm to frosty in the last two years, and where many citizens ridicule the young and unpredictable North Korean leader, Kim Jong Un, the government treated the episode with alarm.

The Chinese news media initially ignored the killings. After they became public, more than a week later, the government said it had filed a formal diplomatic complaint to North Korea and had set up local militias to defend the border.

This month, there were still roadblocks around the area, keeping everyone out except the handful of residents. Local officials, hoping the problem would go away, offered the scantiest of information. And there were no signs of the civilian militias.

A marauding North Korean soldier on the loose in Chinese territory raised some awkward questions about a neighbor that, even during the current period of sour feelings, is kept afloat by China’s largess. How can a nuclear-armed nation backed by China not be able to feed its army, some people asked, especially since the North Korean military is supposed to be a privileged class that gets first consideration in the distribution of scarce resources?

For the North Koreans, the episode was no doubt an embarrassment. The state-run Chinese newspaper Global Times reported Monday that the head of North Korea’s Border Guard Bureau, a senior position held by a general, had been fired in connection with the event.

The soldier was not the first North Korean to cross the border and wreak havoc. In September, a North Korean civilian walked into a nearby Chinese village and killed an elderly couple and their son in a robbery.

Over the past decade, many North Koreans have slipped into China to steal food, and even as Kim has made it more difficult with increased security on his side of the border, they continue to come.

In this latest instance, the fact that the assailant was a soldier raises questions about the feeding and discipline of North Korea’s million-man army.

Overall, the North Korean army is allotted sufficient food, said Joseph Bermudez Jr., chief analytical officer at AllSource Analysis, a consulting firm that studies North Korea. But the distribution system is undermined by corruption, he said, and in some rear areas where supplies fall short, units are rented out as construction workers to earn money for food.

The soldier in this case may have been an officer: Foot soldiers in North Korea do not normally carry guns, Bermudez said. "Only officers typically have pistols, or occasionally senior NCOs," he said, referring to noncommissioned officers. "But he could have been working in an armory and stolen the weapon."

In the triple killing in September, a North Korean man in his early 30s walked into Nanping village on the banks of the Tumen River and bludgeoned to death an elderly couple and their son as they slept, according to a relative of the victims who talked about the killing on the condition of anonymity for fear of angering local officials.

The North Korean killed Li Chunfeng, 63; his wife, Yuzi, 60; and their son, Xianghu, 26, with a hammer he found in their house, the relative said. The North Korean man stole about $100 in Chinese currency, a cash bag from the son’s taxi and two cellphones, he said.

Until recently, North Koreans scavenging for food have been treated kindly. Many of the Chinese along the border are ethnic Koreans who have been happy to give grain and meat, a luxury in North Korea, to the intruders, who then quietly returned home.

From the mid-1990s to the early 2000s, about 20,000 to 30,000 defectors settled in the Chinese provinces bordering North Korea, and they, too, have caused little disturbance.

"Defectors normally wouldn’t stir up trouble. They keep low profiles," said Jin Qiangyi, a professor at Yanbian University in Yanji, Jilin province, who keeps tabs on movements across the border. "Many are women and live in rural villages — they got married and stayed on."

But the two sets of killings and the diminishing economic opportunities from cross-border trade have eroded sympathy for North Koreans. Once considered an asset among locals who traded with the North Koreans along the depressed border area, North Korea has become a liability, they say.

"North Korea is a small country; it’s China’s burden. What benefits can it bring China?" said Dai Jinping, the owner of a car rental company.

An iron ore trading company here, faced with sagging steel production in China, is operating on a reduced schedule, an employee said. The jail in Helong is packed with Chinese drug offenders who sold methamphetamine, known as crystal meth, a debilitating synthetic drug made in North Korea and in wide circulation among unemployed youths in Jilin, locals said. Even the once flourishing trade in expensive seafood — live crabs and octopus imported from North Korea and flown to China’s major cities — is suffering, a victim of the Communist Party’s anti-corruption campaign that has put a crimp on lavish banquets, they said.

The villages of Nanping and Jidi Tun, small clusters of about 20 brick houses, are now abandoned, local people said. The Li couple’s house — with steel window frames and a reinforced front door installed seven years ago after three North Koreans burst into the house and held the family at gunpoint — is now taped shut. The farmland that grew corn, soya and beans lies untended.

The government installed floodlights and cameras in the two villages after the December killing, but no one feels safe, the Lis’ relative said. The state-run China Defense News reported two weeks ago that the government had established and armed local militias to help secure the border, but locals said no such forces exist.

The simple border fence along the Tumen River — strands of barbed wire supported by concrete pillars — is easy for North Koreans to penetrate, particularly in the winter. Chinese border troops are now patrolling the area in sport utility vehicles twice a day instead of once a day, but that is not enough to allay the fear, he said.

The local government’s explanations for how a North Korean was able to enter the village and kill the Lis are not sufficient, either, the relative said. North Korea told provincial officials here that the murderer had been captured. His last name was Lee, and he was 32 years old, the relative said.

As proof that Lee was caught, the North Koreans gave Chinese officials the money, cash bag and phones, and they were returned to the relative.

"We should get compensation for the house and land," the relative said. "This is a tremendous loss economically and emotionally for the family. I asked a Chinese official, ‘Did the family die for nothing?’ He said I should contact the Red Cross to arrange donations."