Depressed people killing themselves as soon as they start to get treatment is a known phenomenon. The energy that comes from treating depression gives them just enough oomph to get to the 'finish line.' It's quite possible they were thinking about it and never told anyone and everyone thinks it's a complete surprise caused by the drug, plenty of people have suicidal ideation or depression while giving zero indication or clues to anyone close to them that would be the case.
Even outside a drug. Breakup happens this can be a result.
Maybe if guns weren’t so accessible people wouldn’t be so quick to use them on themselves in those moments. There’s a statistic out there where a gun in the home is most likely to harm you.