bound to snap

[Mike Hussey]

Abbott: Conklin had these guys wound so tight, they were bound to snap. Bourne was his number one. The guy went for a job, screwed the op, never came back. Conklin couldn't fix it, couldn't find Bourne, couldn't adjust.

What does "bound to snap" mean?

Source: The Bourne Supremacy (a 2004 American action-thriller film featuring Robert Ludlum's Jason Bourne character)

 

[Yankee]

Expected to become emotional, vocally or physically.

 

[Tarheel]

With "bound to" the speaker indicates it was more or less inevitable.