Benjamin Lim at first denied touching an 11-year-old girl in a lift because he was scared.
But after being given 20 minutes to think again by the officer interviewing him at Ang Mo Kio Police Division, the 14-year-old confessed and said it was the first time he had touched a girl and knew that it was "wrong".
He also apologised and promised not to do it again.
This was revealed yesterday on the second day of the coroner's inquiry into his death, when the officer who recorded the teenager's statement took the stand.
Senior Investigation Officer (SIO) Mohammad Fareed Rahmat said that at first, Benjamin, who was taken to the station at 11.15am on Jan 26, claimed he was taking a new route to his home after school on Jan 25, which was why he mistook a different block for his own.
But one point gave him away.
While in the lift with the girl, Benjamin pressed the button for the 13th floor, when he lived on the 14th floor.
SIO Fareed said: "It appeared to me that Benjamin was not being truthful. I asked him to take some time to think about what he would like to give as his account of the events."
When he resumed the interview at around 12.15pm, Benjamin said he had noticed the girl as he was walking home from school and found her "cute". So he decided to follow her.
After getting into the lift with her, he told police he came up with a plan to drop his mobile phone so that he could touch her as he stood up. When he picked up his phone, he used his right hand to touch her left back thigh. He denied he touched her left buttock.
When he exited the lift, the girl said something to him but he could not catch what she said. She then said never mind.
"I am sorry for what had happened. I felt regret for what I did. I just felt the urge to touch the girl on that day. I know what I did is wrong," he stated in his police statement.
SIO Fareed also explained that Benjamin appeared calm throughout the interview and as his statement was recorded. The entire process ended shortly after 1pm.
After the confession, Benjamin was arrested. He was released to his mother's custody at around 2.50pm after she posted bail of $2,000. At around 4.30pm, he was found dead at the foot of his block.
Asked by lawyer Choo Zheng Xi, who is representing Benjamin's family, if the teenager overheard that he was going to be arrested, SIO Fareed explained he had used a code word when asking a colleague to prepare the arrest report, calling it the "alpha" report.
He added that he never accused Benjamin of lying, but told him in general that the purpose of the investigation was to find out the truth.
He also said he followed the procedure set for interviewing young suspects, including questioning Benjamin in an open-plan office.