Based on its shape, the hole could have been caused by a very fast projectile from outside.

Ballistics expert Philip Boyce, who has over 20 years of experience as a forensics scientist, noted that part of the glass inside the window had shattered.

Therefor, he determined the projectile to have been moving very fast.

While he could not determine if it was a bullet without seeing the window himself, Mr Boyce, who specialises in gunshot residue marks, said the crack could also have been caused by a catapult.

"If it was made from a shooting, I would normally expect the projectile to be in the room," he said.

"Dry swabs for chemical testing for copper and lead around the hole could well give an indication if it was made by a bullet," he added.

Mr Boyce is an independent consultant at his own firm, Forensic Scientific, which is based in the United Kingdom.

- Ronald Loh