Did they just bury the baby immediately after the first cough? Yeah... bad joke. Kidding aside, it must be some cruel joke for the parents to leave for their child's survival only for it to die after.
Something that interests me is how the shooter/s weren't even shown. There's never a clear human enemy to blame for the deaths of their group. If there had been any enemies, I think it would've made this arc feel less sad and impactful since some of the focus would go to hating them.