I'm going to not explain why I know so much about this (though the story is actually funny how it got going), but Suicide isn't what you think it is. It starts with dysregulation of Cortisol in the body. Once dysregulated, the mind isn't able to clear out a lot of negative thoughts. Since Suicide is always in the ether, once the idea gets cemented, it starts a negative reinforcement cycle. The point of suicide is to end the pain the thought is causing. (And the pain is very real.) That's why those that survive bridge jumping attempts regret it the instant they jump off, because the pain is relieved when they jump not on their death.
Being a semi-tracking medical issue, there's some realities that'll get you cancelled if you bring them up publicly. There's a natural suicide rate to every society. It's dictated by both Social Pressure and Food Sources. The introduction of high carb diets late in life increases the suicide rate somewhere between 2x to 10x. Wheat introduced to Greenland basically murdered a couple thousand people.
Non-gang related mass shootings are the result of stimulant-based psychoactive medications. But not in the "take pill, go kill" understanding. The pills prevent the person from killing themselves, thus to remove the negative thoughts their mind escalates the "offense" of the suicide. That's when others start getting roped into the event. This is why mass attacks started after the introduction of meth in the run up to WW2. There's also a memetic aspect to them, as the news reports put it in the minds of those that can't remove the thoughts. That's why the introduction of Ritalin to children lead to the school shooting events. The mass events happen after the meds stop working, while at the same time also allowing the person to "get over the edge" and start pulling the trigger. (Meth has been used, since it's creation, in military settings. Most te***r*sts are stimmed off their nuts when they do the acts, for instance.)
Certain other illict drugs also relate. The early introduction of E into the UK created a specific demographic that has a suicide rate double the rest of the population. It was those between 18 and 22 during the "Mad Chester" period. E abuse will also make you far more suicide prone.
There's an inter-relation to PTSD to the topic. PTSD is the radical collapse of at least part of the body's stress response system. It's akin to tearing a muscle. It just doesn't work anymore. There's always a point of too much stimulus and eventually you start to get brutal consequences. This is why the "man just got told he's getting divorced, went to his shed and blew his brains out" events happen. If you hit anyone in a weakened physical state with enough stress, you can generally induce a suicide. (This is clearly understood by the Black Ops world, as a note. Though there's also ways to push someone over the edge, with enough analysis.)
Depression is also completely misunderstood. It's not something that can ever be treated by drugs. It's a protective, neurocognitive state that that body enters to defend the nervous system. It's little different from a cough, a tremor or a rash in the diagnostic sense. It's a blunt response by the body to one of many (often multiple) stressors that it is not currently in a state to fully manage. Which is why the only way to "treat" it is to deleverage the stress and limit stressors while the body recovers.
If you know someone struggling with depression, the best advice I can give is to help them start a walking/exercise routine and move to a ketogenic diet. While Keto isn't a perfect answer, it'll do the majority of the work. Once they're in a better place, it's highly advisable to get a full endocrinology checkup. There's a reason Vitamin D and Testosterone are known anti-depressants. They're regulated as part of the HPA Axis.
Also related, that's why trans are so suicidal. They're the highest category for being suicidal before they suddenly start wanting to be something else. They just have full cycle HPA Axis dysregulation. (No one is quite at the point to openly discuss infectious agent issues related to all of this, but that's likely to be a strong source.) Since it's a hot-button topic, useful technical medical studies are basically worthless for the time being. Even most non-controversial medical topics are prone to severe political correctness. (Was once reading a report on ADHD and it took me a solid 30 minutes to unwind what they were dancing around. 50% ADHD children have mothers are that wrecks in their home. That's literally their only issue.)
As for the delayed, to lots of people suicide notes, the reason should be pretty clear from my explanation. It's roping others into the event to push the person over the edge. It's one of the most horrifically selfish things a human can do. It's horrible. But it's also perfectly logical to those in the actual "death spiral" that is the suicidal ideation loop. Oh yeah, Suicide by Cop is the same thing, just a different personality type. (The "bring others into my suicide" logic is subject to a lot of personality realities of the person & what they're involved in, in life.)
Edit: 2 other points. "I can take away the pain" is something of a classic cult recruiting pitch because that's what the suicidal are actually looking for. I wouldn't recommend that path if you're trying to talk someone "down from the ledge", but there's a harsh reality to the appeal to those in a bad spot. The other point is that youth suicides appear to be mostly a post-WW1 or post-WW2 reality. This one appears to be fairly hazy because "data issues", but it's also possible given the time period that they were never reported as such for the longest time. It's probably important to realize the way you used to deal with mental illness was shoving someone in an actual closet regularly to keep them out of sight. There's a reason that phrase exists.
