Just a quick question: How did Robin's folks die?

Is it a set in stone answer, like how Bruce's folks died, or have there been several different storylines with the same basic result?

Thanks.

VirginiaR.
"On the long road, take small steps." -- Jor-el, "The Foundling"
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"clearly there is a lack of understanding between those two... he speaks Lunkheadanian and she Stubbornanian" -- chelo.