wouldn't it be "lose"?
Lose is present tense. It would then translate to: ...verlieren ihr Leben.
Does this phrasing sound natural to native-speakers? I have heard other phrasings much more commonly, for example viele Menschen sind ums Leben gekommen.
I have heard kamen ums Leben.. Yours is the perfect form so would say it was but I'm certainly no native
Is this an example of 'distributive singular' for ihr Leben?