I’m not even sure if she chose to leave and they decided to kill her off because she ticked someone off or it was her idea. Or they told her she’s being killed off without her wanting to leave.
Lucy (https://er.fandom.com/wiki/Lucy_Knight) you could argue, became a fan favorite character, (https://en.wikipedia.org/wiki/Lucy_Knight) as the new young doctor on the show (https://web.archive.org/web/20140401074114/http://forums.televisionwithoutpity.com/topic/3116836-er/?view=getnewpost). And Kellie Martin was a big TV star at the time with Life Goes On and Christy under her belt.
And then, this episode aired (https://web.archive.org/web/20061031125154/http://www.jumptheshark.com/e/er.htm), where Dr. Carter gets attacked by the crazy patient and then when he looks over and sees Lucy there, bleeding to death, with no one knowing. That was such a stomach-churning shock to the viewers at the time.
The next episode (where she does die) brought in almost 40 million people to see what happens to her.
Lucy Knight's Shocking Death On ER May Not Have Sat Well With Fans
(https://www.looper.com/1136983/lucy-knights-shocking-death-on-er-may-not-have-sat-well-with-fans/)
BY JULIA SELINGER/DEC. 18, 2022 5:00 PM EST
For a time in "ER," being a doctor at Cook County General Hospital meant you could do your job relatively unscathed. Sure, there were the emotional battle scars and mental health tolls. Still, the medical drama series didn't rack up nearly the body count as "Grey's Anatomy," the heir apparent to "ER," insofar as the hospital staff was concerned.
That changed in Season 6 when Lucy Knight met her grisly end at County General. Knight, played by Kellie Martin, joined the cast of "ER" (https://www.looper.com/248450/what-happened-to-the-cast-of-er/) in Season 5 as a third-year medical student under the tutelage of Dr. Carter (Noah Wyle), a second-year resident. In "Be Still My Heart," a troubled law student named Paul Sobriki (David Krumholtz) savagely stabs Lucy and Carter. In the next episode, Lucy succumbs to her wounds.
While Knight wasn't the first staff member to die during their time at County General (that honor goes to minor character Dennis Gant, played by Omar Epps, who was killed in a train accident), her death was shockingly violent and treated as a major television event. For some fans, Lucy's death went too far (https://www.looper.com/723892/times-er-went-too-far/).
Lucy's grisly death traumatized some fans
When Lucy was stabbed in Season 6, the cliffhanger ending did wonders for the next episode's viewership. "Almost 30 million people tuned in on Thursday night to watch 'ER,' Kellie Martin told Entertainment Weekly (https://ew.com/tv/2018/03/30/er-oral-history-lucy-carter-stabbed/). "I was happy and honored, yet at the same time ... wondering what I had done to deserve such a big demise. I mean, it was pretty brutal."
"Be Still My Heart" and "All in the Family" may have attracted scores of "ER" fans, but some agree that the storyline was hard to stomach even for a gory medical drama. "Lucy's death traumatized me," wrote Redditor u/NeverFainted (https://www.reddit.com/r/television/comments/6yi2b7/comment/dmnkwhu/) to a flurry of upvotes. u/Copywrites (https://www.reddit.com/r/television/comments/6yi2b7/comment/dmnla34/) felt similarly, adding, "It really left a bad taste [in] my mouth as a kid."
To see a doctor in "ER" and experience that horrific level of violence was unprecedented. But as some fans point out, Lucy's death opened the floodgates for other staff members to die in increasingly outlandish ways, be it a helicopter accident or ambulance explosion. "When Lucy died, it was shocking and tragic," wrote u/DaveSW777 (https://www.reddit.com/r/television/comments/6yi2b7/comment/dmof62a/). "By the final season, the show was a bloodbath."
The shock value never wore off for some "ER" fans. "To this day, I have people coming up to me," said Martin. "They'll get ashen when they see me sometimes because it was such an amazing two episodes."