Nearly a week has passed since the former US President and Republican Party nominee narrowly escaped death, instead receiving minor injury, when a bullet grazed his right ear at a rally in Pennsylvania.

One person attending the rally died after also being hit, while the 20-year-old shooter -- whose motives remain under investigation by the FBI -- was killed by counter assault teams.

Security officials have been under pressure to explain why the gunman was able to position himself on a nearby rooftop.

It was the first time since 1981 that a leading US political figure has been shot, although four US presidents have been assassinated in the course of history.

After 9:50, we learn more from the organisers of a new exhibition promoting polar research.

9:00am - 9:45am: Trump shooting
9:05am-9:50am: former US Secret Service Officer who protected several presidents from Reagan to Bush. He now is President of security firm Lowery & Associates Consulting
9:05am-9:30am: Steve Vickers, CEO of risk consultancy Steve Vivkers & Associates; he formerly commanded the Criminal Intelligence Bureau of the Hong Kong Police Force
9:30am-9:50am: Dr LJ Punch, Critical Care surgeon and founder of the Bullet Related Injury Clinic in St Louis Missouri

9:50am-10:00am: Nature and Polar Safety Education Exhibition

9:50am-10:00am: Dr Ho Kin Chung, Founding Chairman of the Polar Research Institute of Hong Kong