Police say the incident occurred in the Pora Maath area of the port city’s West Madarbari on Saturday night.
The deceased has been identified as Bali Begum, 25. Her mother Baby Akhtar, 50, and older brother Md Sumon, 28, were admitted to Chittagong Medical College Hospital with injuries.
Police have arrested Joy, 19, his brother Ekramul Haq, 18, and their mother Mita Begum, 44, over the incident, said Sadarghat Police Station Inspector Ruhul Amin.
The two families were neighbours, he told bdnews24.com. A few days ago Ekram stole Sumon’s mobile phone. Though he returned the phone afterwards, he kept the memory card.
Mita and Bali argued over the memory card’s return on Saturday night. Joy stabbed Bali with a knife during the argument. Sumon and Baby were stabbed by Ekram when they tried to help Bali.
Bali, Sumon and Baby were taken to Chittagong Medical College Hospital, where doctors declared Bali dead, said CMCH Medical Outpost ASI Alauddin Talukdar.
Police detained Joy, Ekram and their mother soon after the incident. The knife used in the attack was also recovered.