However, Sheriff Diaz did know that Alex was involved. In the end, he told Deputy Standall that everything about the Bryce Walker case was going into permanent storage. It was a hint that Diaz knew Standall destroyed evidence to protect his son, and Diaz was going to go along with that.
As for why he would do this...well, it's possible that he felt like he had no choice. When Standall came to see him after finding out that Alex was alive, Diaz told him not to worry about it and then hung up on him. Maybe he felt like Standall would just kill his son anyway, so there was no use fighting against it.
Sheriff Diaz may have known what happened to the evidence, but he didn't tell anyone else. He must have been afraid of getting in trouble himself. After all, if anyone found out that he knew what happened to the evidence, he would be in big trouble since destroying evidence is a serious crime in itself.
In conclusion, Sheriff Diaz knew that Standall destroyed evidence in the Bryce Walker case, so he went along with it. He might not have liked this decision, but he couldn't change it.
As the fourth season begins, Alex's father, Deputy Standall, is aware of his son's involvement in Bryce's death as well as his son's drug addiction. When Standall confronts Alex about his actions, they have a heated argument which leads to Standall shooting and killing him.
However, this isn't the first time we've seen something like this happen between them. As you may know, Alex's mother, Elizabeth, was also killed by Standall when he found out she had another man over for dinner while he was away at school. This makes Alex want to take revenge on Standall for murdering both of his parents.
Now, it turns out that Alex wasn't even there when his parents were murdered. His friends try to tell him this, but he doesn't listen to them. Instead, he goes after Standall alone. Once he finds him, he shoots him several times until he dies.
Alex then calls nine-one-one and tells the police that his father has been shot. However, instead of taking him to the hospital, they take him to jail where he receives three years' probation.
After this incident, Alex decides to quit drinking and using drugs. He moves out of his parent's house and starts looking after his younger brother Daniel.
Clay and Ani discovered Alex did it and assisted in covering his tracks in the last episode of the third season. Ani completed her statement by stating Monty murdered Bryce, and Deputy Standall informed her that Monty was murdered in his prison cell. This means that both Alex and Monty are dead.
However, later in the episode she meets with an unknown person at a restaurant who tells her not to worry about Alex. This leads many fans to believe that perhaps Bryce is still alive and this was just another attempt to get information out of Ani.
Unfortunately, we will never know for sure what happened to Bryce, but this does show that he still lives on as a character in the series.
The terrible thing was that Alex was shot and we didn't know for sure if she died or simply passed out unknowingly. Walker intended to ask Alex something (marry him) after she was shot during a wedding, but it didn't happen until she was in the hospital for a few days. When she woke up, Walker was gone. He left Dallas behind and took off with all his money. This is where the story really takes off: detective work! You see, there were some witnesses who saw someone else get away with Alex's car. And also, somebody had broken into her house and stolen her gun. So police suspected someone else of being involved in the crime.
When Alex got better, they went to Dallas to search for Walker but he had disappeared. Then one day, when Alex was walking through the park, she was shot by an unknown person. She died at the scene. The killer then stole her car and drove off. Police suspect this may have been done by someone wanting to harm Alex but not knowing that she was still alive. After her death, her father came to town looking for evidence that could help find who killed his daughter but couldn't find anything useful so he returned home sad.
Meanwhile, Detective West is assigned to investigate the case and finds evidence that points toward Ranger Daniel Jackson as the shooter. Jackson has an airtight alibi though - he was in prison at the time of the murder.
Spoilers for 13 Reasons Why: Who Killed Bryce Walker? Bryce Walker drowns in the river in 13 Reasons Why season 3. After a struggle with Zach, Bryce is severely injured and abandoned on a pier near the river. Alex Standall arrives at the scene, accompanied by Jessica Davis, whom Bryce had phoned to speak with. Despite being told by both women that everything was okay and they should go home, he doesn't believe them and decides to check up on them later.
Bryce's body is taken to the hospital where Dr. Dan Fielding performs an autopsy. His conclusions suggest that maybe not all of the people involved in Bryce's death were aware that he had died. As the police start to investigate this new lead, they come across another girl named Cassie who claims to have information about the night of Bryce's death. When Detective Jim Valenti interviews her, she tells him that she saw Bryce get into a fight with someone at the party before he disappeared. She can't remember who it was though, because she was too drunk.
Valenti talks to several more people at the party who say that they didn't see anything suspicious but admits that it might be hard to find the person who killed Bryce since everyone there knew each other. He then asks Jessica if she knows of anyone who would want to hurt Bryce but she denies knowing anything about him getting into a fight at the party or why he would have gone outside alone later on.