Years ago, when I took benzos I preferred long-lasting ones like Diazepam or Clonazepam to short-acting ones like Xanax. The long-lasting ones are less addicting (but highly addicting nonetheless). They let you down gently, Xanax dumps you off a cliff. Indeed, the first step to wean yourself off benzos is to switch from a short-acting one to long-acting one, and only then gradually reduce the dose.
But more relevant to this thread: Benzos can
definitely make you unreasonably angry and violent. Most drugs, benzos included, can induce effects opposite to those intended. So antidepressants can make you the opposite of happy (suicidal/homicidal), and benzos can make you the opposite of calm (nervous/jittery, or even angry/violent). This is especially true during withdrawal, but it can also happen while taking the drug. Fun story (not), years ago in a moment of clarity I quit R.I. and had my original account (Monster) closed because I said something rude and out of character to someone on this board while I was withdrawing from benzos. The withdrawal was making me crazy, and I had a super low frustration tolerance.
That being said, my guess is Paddock obtained the pills to help him sleep and keep calm during the massacre.