Some agents stipulate that they don't want to even look at stories where children are killed, abducted or injured. That seems a little sensitive to me, since there are plenty of classic works where underage individuals suffer horribly, and sometimes even die (I mean, Jo's sister died in
Little Women). I mean, who wants to write a story with children as support characters if all they do is hang around in the background being "twee" or if there is absolutely no hardship or risk experienced by child protagonists? For heaven's sake, even Harry Potter has some suffering and death on the parts of kids in the story, and it's written for kids! A child running away from an abusive situation (and temporarily landing in something even worse) is a classic trope in fantasy and many other genres.
Having said this, I tend to be a bit more protective of kids (and animals) as a reader and writer. Maybe it's something to do with how we're wired as humans. We want to protect the helpless and so are especially distressed when they die in stories. This desire to protect the helpless can be used to create tension and to raise the stakes for characters, though.
I personally think that if the death advances the plot and is not portrayed in a lurid, gratuitous way that's simply meant to titillate or horrify, then it's probably fine. It certainly sounds like something that would whip your character into action in a way that most of us could relate to.
Some readers do get angry over the death of a character they like, but if it's clear that the death was important to the plot or accomplished something important, most "forgive" the writer.
I tend to get "mad" at writers for killing characters when I either feel they're doing it simply because they don't want to bother with the character anymore or because they're doing it simply for shock value or to make you sad without its having a real impact on the story itself.
I really don't like it when writers kill the protagonists off at the end of a series as a way of making it clear to fans, agents and editors that they are absolutely done with writing anything more about these characters. I think there are more satisfying ways of giving a series closure than that