However, one of the most talked about episodes of the season, which proved to be a catalyst for the dramatic events which followed, was episode six, in which Liberty High was on lockdown following a code red announcement – an active school shooter.
The contentious episode, titled Thursday, saw the students try to work out whether it was just a drill, whether Tyler was responsible and whether they would make it out of school alive.
With a lot going on during episode six, here's a quick explainer of what happened...
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What happens in 13 Reasons Why episode 6?
The episode begins with what looks like the aftermath of Clay and Zach car crash from the episode before – Zach is bleeding out on the floor while Clay and Justin are struggling to save him. However, this turns out to be another hallucination of Clay's – they are actually in the middle of a training exercise, in which Clay and Justin are trying to stop a dummy from bleeding.
During the exercise, Tony, who is paired with Tyler, is suspicious of how much he knows about guns and the types of wounds they can cause. In the previous episode, he saw Tyler appear to be buying illegal guns at the dock.
Clay talks to Zach, who has been recovering from the car accident from the episode before. Clay, who had been driving the car and crashed it, tells Zach that he can't remember what happened, with Zach replying: "You mean after you crashed my car and ditched me?" He then tells Clay to stay away from him.
Afterwards, Clay meets the new Dean of Discipline, Hansen Foundry, who seems to be closely surveilling the students and investigating the destroyed security cameras around the school. Clay then bumps into Jessica, who says that she saw him on the list of students who received an interview for Brown University. He begins to panic as he doesn't remember sending in his admission essay, in which he wrote: "I covered up a murder."
As Charlie, Alex and Tony are studying Spanish, the principal announces a Code Red, which is a non-drill school shooter lockdown. While the students think it is a drill, their supervising teacher Foundry doesn't appear to have expected it and tells them to barricade the doors. Tony notices that Tyler, who was previously studying in the next room, is no longer there and Tony begins to suspect that he is the active shooter.
Meanwhile, the football team are hiding in the locker rooms. Justin asks their coach if the shooting is just a drill, but he doesn't seem to know. Diego wants to go outside and fight the gunman, but Justin tells him he's being stupid which leads to an argument. After Diego taunts him about Jessica, Justin leaves the locker room to find her.
Clay locks himself in a classroom and texts Tyler to check if he's ok, but he doesn't respond. He then begins to see hallucinations of Monty and Bryce, who taunt him by saying that the shooter is Tyler and that Clay stopping his last school shooting attempt was a waste of time. Although Clay still thinks the shooting is a drill, someone begins tugging at the door handle of the class room and banging on the door.
Zach finds himself barricaded in the photography room with Winston and they decide to take marijuana gummies. After seeing what looks like a gunman outside their classroom, Zach reveals to Winston that he beat up Bryce on the night he died, but did not kill him as he died from drowning.
Tony, Alex and Charlie look in Tyler's bag and find multiple photos of guns. Tony wants to turn them in to Foundry, saying that if Tyler is in fact the shooter, it would be Tony's fault for not telling the police about his previous attempt. However, Charlie and Alex tell Tony not to, arguing that if the shooter isn't Tyler, he'll be taken in by police and he may reveal Alex as Bryce's killer.
Estela, who has been hiding in the girls' bathroom, finds Tyler in one of the stalls. They talk about her brother Monty, who sexually assaulted Tyler, and become friends.
After hearing gun shots, Tony hands in the photos to Foundry, who says he will look into it but doesn't appear to be doing anything urgent with the new information. Alex suffers a panic attack as Charlie tries to calm him down.
While Jessica is hiding in the HO room, Justin climbs in through the window. They reconcile and kiss, even though Jessica is dating Diego.
Clay leaves the classroom, but is confronted by a gunman with his face covered. Just before it seems as if he's about to be shot, the gunman reveals himself to actually be Clay – he's just hallucinating. The principal pulls a panicked Clay into his office to hide out the rest of the lockdown.
The lockdown ends, with staff giving the all clear. Alex kisses Charlie after he spent the lockdown calming him down.
Is the school shooting real?
After the lockdown ends, Clay walks out of the principal's office to see that the shooting was just a drill, and that a security team was called in to make the drill more realistic by firing rubber bullets and banging on doors.
Clay starts shouting at the principal in front of the whole school, telling him that the drill was cruel and unnecessary. A security guard grabs him but Clay grabs his gun and starts waving it around. After a minute, he starts to put the gun down but is tackled to the floor by a security guard and knocked out with a baton.
He then wakes up, handcuffed to a gurney which is transporting him to a mental facility as his fellow students watch.
Why did everyone suspect Tyler was the shooter?
During season two, Tyler was sexually assaulted with a broom by Monty de la Cruz. The incident traumatised Tyler and sent him into a spiral of depression, culminating in him attempting a school shooting at the end of the series.
Before he could enter the school dance with his guns, Clay managed to stop and disarm him. Tony then drove Tyler away to evade police while Clay hid his guns.
Throughout season three, the group kept an eye on Tyler as they tried to help him out of his dark place. By the end of the season, Monty had been imprisoned for sexually assaulting Tyler and Tyler had recovered. He created an exhibition full of photos of his friends in order to thank them for helping him.
During the season four school shooting, Tony, Clay and Justin were still suspicious of Tyler, as he was seen talking to a gun dealer at the dock and keeps speaking to the police. While Tony worries that he has slipped back into the dark place he was in before, it is revealed in a later episode that Tyler is actually working with the police to catch a man who was illegally selling guns.
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