Yeah, murder-suicide...riiiight.
Not told the whole truth...either the daughters comments indicate she is a loon or severely grief-stricken...or, put in proper context, if the kids have reason to believe it was meant to look like a murder-suicide, then wishing "mummy & daddy" to be together makes sense...
Oh heck, like the others, we'll never really know...suspicious or not, a good assassination always takes the guise of an "accident/tragedy"...