Xu Zengzhi is in custody after allegedly killing two children and injuring four others. [Photo: weibo.com/Pizhou Public Security Bureau]

The suspect who was arrested Sunday in Beijing for brutally killing two and injured four children in east China's Jiangsu Province is said to have killed his father-in-law and injured the other two.

The 91-year-old elderly man named Lu Qiyin was killed, while his wife and one-year-old grandson were injured with the toddler still in a critical condition.

Jiangsu Police has confirmed the suspect is Xu Zenzhi, the son-in-law of the victims.

Xu is also suspected of killing two children and injuring four others in the village of Pizhou City.Xu is said to have been at odds with the elderly couple for a long time because they objected to him beating up his wife.

The report of Chinanews.com cited Zhang Genhua, the relative of the victims as saying after Xu got married, he regularly beat his wife who finally ran away from home two months ago because she could no longer tolerate the domestic abuse.

Since then, Xu frequently came to the home of his father-in-law to look for his wife as he believed his wife was hiding out in their home.

Zhang said that "Xu thought the family of his wife was trying to break them up and were hiding his wife from him, so he always lost his temper as he couldn't find his wife."

Two weeks ago, Xu had a fight with his wife's brother over his wife. "Maybe the conflict triggered Xu to resort to murder", Zhang added.

In the evening of the same day, Xu allegedly killed two children and injured four others in his village, two hours after murdering his wife's family.

According to the police, he killed the two children because he believed his neighbors persuaded his wife to run away from him, so he attacked his neighbor's kids in order to inflict revenge.

Xu was caught by police at a railway station in Beijing on Sunday.

The investigation into the two murders is continuing.