u wont see SOF because when u see them, u r already out of your
body. 
it is possible for a sniper to take out VIPs. however, it is not
probable. u have to consider the threat level (which im sure ISD
has that figured out).
whether people have access to weapons (no)
how possible is it to have access to "one of those windows", which
happen to be offices.
how possible is it for the sniper and his spotter to evade CCTV and
security in the building, followed by how they access the offices
without tripping alarms and/or showing on CCTV.
as for bombs, it is relatively easy to create explosives and/or
incendiary materials. but be rest assured that Singapore is being
protected 24/7 by professionals (NSF and Regulars) specialising in
this field of work. and, im sure intelligence units from the Army
and Police has this area figured out also.
less a suicide bomber in a car, who ram pass the cordon... survived
the shooting by our SPF and all the crap and then still manage to
detonate the device.
so, just sit back and enjoy the show. the aim of terrorism is to
get u to fear a couple of sh!tbags anyway. if they succeeded in
that, terrorists win already.
