Spoilers for episode three ahead!
9-1-1 season six continued on Monday night with a gripping third episode that some viewers have branded "disturbing" and "dark".
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The latest instalment delved into Athena's past as she and her husband Bobby led an investigation into the murder of her childhood friend, Tanya Kingston, from 45 years ago.
WATCH: Are you enjoying the new season?
While Athena initially suspected that it could be her own father who was responsible for Tanya's disappearance, a key piece of information from the victim's sister, Joanne, led the field sergeant to the real killer.
A sequence of tragic flashbacks revealed Junior Franklin to be the murderer and viewers watched as he followed Tanya into an orange grove, chasing her down and ending her life.
MORE: 9-1-1 star Jennifer Love Hewitt shares poignant message with fans ahead of new episode
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In the present, Athena and Bobby tracked Junior down and ended up chasing him through the same orange grove. Athena finally caught up, hitting him over the head and telling him: "All this time you've been hiding in plain sight for 45 years. But I got you. I got you."
Junior Franklin was revealed as Tanya's killer
Viewers took to Twitter to comment on the "disturbing" episode, with many left reaching for the tissues. One person wrote: "#911onFOX was really good tonight but very sad! I hate what happened to that little girl that scene of her crying and running from dude in that dark, foggy field was heavy. I was ready to cry," while another added: "#911onFOX got me crying real tears, such an emotional scene in that orange grove."
A third fan commented: "The scene in the orange field destroyed me emotionally #911onFOX," while another tweeted: "This episode really took a toll on me #911onFOX."
Viewers praised the emotional episode
Other fans simply praised the brilliant episode, with one person writing: "What an emotional, moving episode tonight. Outstanding. Heartbreaking," while another added: "That was an EXCELLENT episode of #911onFOX!"
Peter Krause, who plays fire captain Bobby Nash, spoke to EW about the "darker" episode ahead of its release. "One of the great things about the type of storytelling 9-1-1 is doing is that it's not just about the big emergencies or tidal waves," he said. "Every now and then there are some crime-solving mysteries. This one is a little bit darker than we normally go, I would say — you know, it's a real murder mystery."
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