Just three seconds after Corporal Kok Yuen Chin fell into the Tuas View Fire Station pump well, a fellow Singapore Civil Defence Force (SCDF) officer gave instructions in a panic for another to enter the well to save him.

The phrase "Go down, faster", in Mandarin, is heard repeatedly in video footage that captured the last moments of Cpl Kok, 22, before he was pushed into the 12m-deep well on the night of May 13 last year.

The instruction was directed at Cpl Sok Leng, a swimming instructor who was told to be on standby in case anything went awry, Staff Sergeant Ng Meng Kiat told the court yesterday.

Testifying during the ongoing trial involving two SCDF officers linked to Cpl Kok's death, Staff Sgt Ng said he gave the instruction so quickly after the full-time national serviceman fell into the pump well out of "instinct" when Cpl Kok did not resurface.

Cpl Kok was pushed into the pump well in a ragging ritual that was part of activities to mark the completion of his national service.

Kenneth Chong Chee Boon, 38, a lieutenant, and Nazhan Mohamed Nazi, 40, a first senior warrant officer, were rota commander and deputy rota commander, respectively, and were in charge of the station that night. They were each charged with aiding a rash act that caused grievous hurt by illegal omission.

The duo had allegedly failed to prevent a group of officers from making Cpl Kok enter the pump well, thereby endangering his life.

After Cpl Kok fell into the well, the group gathered there mounted a rescue operation where some, including Staff Sgt Ng, entered the well while others used equipment to pump water out of it.

Staff Sgt Ng was the one who found and retrieved Cpl Kok's body.

The group managed to pull Cpl Kok out of the well but, by this time, 36 minutes had passed and the Malaysian national and Singapore permanent resident had drowned.

In security camera footage before the push, Staff Sgt Ng is seen running ahead of the group carrying Cpl Kok and opening the pump well's gate. When asked why he did this, he said he thought they were playing a prank that would stop if Cpl Kok chose not to enter the well.

Also taking the stand yesterday was Sergeant Mohamed Hanis Mohamed Hussain, who was not present when the group began carrying Cpl Kok to the pump well.

When the officers on duty gathered in the control room for the cake-cutting ceremony for Cpl Kok, Sgt Hanis said he remembered people talking about the "kolam", which refers to the pump well in Malay.

While he understood the "kolam" to refer to a ritual that involved putting people in the pump well, he said he was not concerned at that point. "I felt that we were making fun of each other," said Sgt Hanis, who left the room after the celebration. When he returned to the room after about five minutes, he saw only Chong, who left a few minutes later.

Sgt Hanis realised that something had happened only when he saw people running in the yard.

Earlier, witnesses had testified that at some point in the night, Chong had stuck his head out the room window and told those at the well not to film the incident. However, Sgt Hanis did not recall this.

The trial continues today.