A disgruntled patient in Hefei, the capital city in China’s Anhui province, killed a nurse and injured four others with a kitchen knife on Tuesday morning, New Anhui Evening News reported.

The male suspect is believed to be a former patient at the Second Hospital of Anhui Medical University. Two of the four injured nurses were critically injured, said the report.

The reason for the attack remains unclear. According to several accounts on Sina Weibo, the hospital had stopped treating the suspect after he failed to pay fees.