I'm like only halfway invested in this show, but even I'm upset with killing off Sara.
Same thing happened when they killed off (in a horrific manner) the female love interest on Prison Break. The producers were bragging about how they killed her "awesomely", while being completely tone-deaf to how much the character was liked. (They eventually backtracked and brought back the character.) Do TPTB really not realize no one wants to see great character horribly murdered??
It's ridiculous. They brought in this awesome, heroic (well, she worked with the good guys) character that was well-recieved; she wasn't even around that long, and they kill her off.
This also reminds of Person of Interest, in which they killed off a female character who got replaced by another. At least Carter had an exit arc and went out like a Boss.