A district judge, in sentencing a bank officer who fired a shot at a passer-by with an airsoft gun, made clear a jail term was needed to deter other people who might have the same idea.

DJ Siva Shanmugam said sending the offender Ernest Sim to jail was to ensure the maxim "once bitten, twice shy" was not lost on him.

Sim, 26, a personal banker, was jailed seven weeks and fined $12,000 in August for firing a shot from his pellet gun at a passer-by, and possessing an airsoft pistol and importing an airsoft pistol in December without a licence.

Five other charges were also taken into consideration, which included separate incidents involving two other victims.

In the shooting incident, which occurred at about 8.15pm on Jan 26, Ms Bian Xin, 29, was hit just above her chest by a white ball-shaped pellet while walking along a sheltered area near Block 101, Clementi Street 14. It later emerged that the shot came from the second-storey unit of the block, where Sim lived.

Ms Bian had noticed that the lights in the unit went out immediately after she was hit.

Police checked the flat and seized an airsoft gun and airsoft pistol, for which Sim admitted ownership. Sim said he bought the items in Thailand last December, dismantled the guns and hid the parts in his bags to get them into Singapore via Changi Airport. He did not have a licence to import or possess such items.

His lawyer Lee Ee Yang urged the court to impose a non-jail sentence, pointing out that Sim was remorseful, no significant harm was done to the victim, and Sim had made $1,400 in voluntary compensation to all the victims involved.

But Deputy Public Prosecutor Chan Yi Cheng called for a jail term of at least eight weeks for the shooting offence, saying that Sim had targeted the victim, had done so out of boredom and mischief and had shot at two other victims, as reflected in the other charges taken into consideration.

DJ Siva Shanmugam, in explaining why the deterrence was necessary, said most people live in high-rise buildings and are close to each other. "It would be relatively easy for someone to perch themselves in their apartment and take potshots at passers-by without being detected," he added in judgment grounds released last week.

He noted that Sim had turned off the lights in his home immediately after shooting to escape detection.

DJ Siva said the offences were premeditated and well-planned, noting that Sim would have undertaken the necessary prepatory acts which aggravated the offences.

The offence was also not a "one-off incident" as three other charges showed he had discharged pellets from his airsoft gun on three different dates in January. Sim has paid the fines and is on bail pending his appeal on the sentence.