It was their daily routine to try to reach him over the phone, after Sadman Sakib Rafi went missing on January 13 this year.
On the 14th day since he couldn't be traced, the family again called his number and this time a woman answered, saying she did not know Rafi but found the SIM card at Hatirjheel lake while cleaning the area.
Informed by the family, law enforcers interrogated the woman but could not find any clue leading to Rafi, his mother Monowara Hossain said.
After waiting for three more weeks, Monowara on Monday thought there might be clues in the Hatirjheel lake area as her son's SIM card was found there.
She did manage to trace him -- his corpse unclaimed and already buried.
A body recovered from Hatirjheel lake on January 14, a day after Rafi went missing, was her son.
"I thought my son went through Hatirjheel as his SIM card was there. I decided to look for my son and ask everyone, even muggers in the area, showing his photos," she told The Daily Star.
The mother went to Hatirjheel police for help. A police officer listened to her and showed some photos of an unclaimed body they recovered.
"The body in the photos was swollen but still I found similarity with my son. Then they brought his clothes and shoes [police preserved them as evidence]," she said.
"The shoes belonged to my son. He left the house wearing the shoes on January 13… My son was killed that night," the sobbing mother said.
"Law enforcers could not identify the body, and it was left unclaimed for a month at the hospital… What's the distance between Hatirjheel and Bhatara police stations?" she asked.
Sadman's mother earlier filed a missing person's case (GD) with Bhatara Police Station in this regard.
"Law enforcers repeatedly told us that my son might have joined a militant group. They told us that my son might be taking the training. I repeatedly told them that he could never join a militant group," she said.
"What an unfortunate mother I am that I can't see my son's body," she lamented.
The family is now trying to locate Rafi's grave with the help of Anjuman Mufidul Islam which buried the body.
According to the GD, Sadman left the house on the morning of January 13 without informing anyone. His mobile phone was found switched off.
Monowara earlier said that her son returned to Dhaka from Malaysia in September 2019. But he could not go back to Malaysia due to the coronavirus situation.
Among three siblings, Sadman is the youngest. He was born and raised in Saudi Arabia. He was admitted to APU in Malaysia three years ago.
SI Hafizur Rahman of Bhatara Police Station, who was in charge of investigating the GD, said they had tried to locate Rafi using technology, but failed.
SI Harun-or-Rashid of Hatirjheel Police Station said the woman identified the unclaimed body seeing the photographs and clothing.