What does 「まさかそれが、」 mean at the beginning of this sentence?


> **まさかそれが** 、あのような惨劇{さんげき}を引{ひ}き起{お}こす事{こと}になるとは、知{し}るよしもなかったのです。

What if 「まさかそれが、」 is at the beginning of a sentence? What does it mean? Would
it mean something like "That's it,"?




まさか is a _guiding adverb_ that leads to an expression of something unexpected.
それが is the subject for the verb 引き起こす.

