A friend of Zhao Dengyong, the man Yunnan police say deliberately set off an explosion that killed four people, said he witnessed a middle-aged man give Zhao money and knapsack that likely contained the bomb.

Lin Guocai told the Guangzhou-based newspaper Southern Metropolis Daily he believes Zhao was duped into carrying the bomb that was then remotely detonated when he reached the intended target .

The explosion occurred May 10 and police have labeled Zhao as the intentional bomber who took his own life and three others. Sixteen people were injured in the blast, several of them seriously.

The explosion happened at a community hall where local people were signing compensation agreements for the demolition of their homes in Baihetan township of Qiaojia county

Video footage shows that at 8:59 am, Zhao wandered into the yard of the community hall wearing a knapsack. Five minutes later, Zhao was seen entering the building shortly before the explosion. 

Following the explosion, local police announced that Zhao was the bomber and he was intent on "taking revenge on society" even though his home was not being demolished.

Zhao's family has never believed the police's portrayal of Zhao as someone who was intent on committing murder.

"My younger brother brought the bomb to the office without knowing anything about it. He was certainly used by others," Zhao Dengji told the Global Times yesterday. "My brother did not have a knapsack. We hope the whole picture of the accident can be made clear as soon as possible."

Villagers in Qiaojia said there have been many disputes over compensation for land deals.

"According to the video, the conclusion the local police have reached is suspicious," Cheng Lei, a law expert with the Renmin University of China, told the Global Times after the video was described to him.

Zhao Dengji said local police have repeatedly told him the case is still under investigation.

"Police told me to prepare a funeral for my brother, but we have no money to do that. My brother has a one-year-old baby. How the child will be raised has not been settled," he said.

Calls to Lin Guocai and Wen Qicong, a vice magistrate of the county, as well as the local public security bureau yesterday went unanswered.

A rumor has been spreading that suggests local authorities gave the family of a mother and child who were killed just 30,000 yuan ($4,743) in compensation to cover funeral expenses. The family of a government official who was killed in the blast is likely to receive 1.6 million yuan in compensation, a Tencent microblogger named "xinwenge" said.

Cheng Shuli contributed to this story