The law can't compel you, unless in certain professions, to assist, aid, or rescue others.
That said, before any legal duty can be breached, (assuming ne attaches) one must be present.
No one can determine what another person knew, so even if a legal duty had attached, did person X; know person Q required assistance?
This is a very sticky wicket you broach.
You'd have to show any if those mentioned knew person X had been attacked and required assistance, and the people mentioned owed X a duty to act. Simp,y put, they owed X no duty to act.
A security guard's main duty, as spelled out in your Cal Code is simply to "observe and report".
What are a security guard's ROLES AND RESPONSIBILITIES?
A security guard's role is to PROTECT people and property of his employer or contracted clients.
A security guard's responsibility BEFORE an incident/offense has occurred is PREVENTION.
A security guard's responsibility DURING or AFTER an incident/offense has occurred is to OBSERVE and REPORT.
http://www.security-guard-training.net/responsibilities-security-guard.htm