Let's take this to the extreme:
You are a man in the Arctic, wronged by your lover who fucked some stranger, and drunk. You are angry and react without thinking so punch the fuck out of him. People hold you back.
You are a man in the USA, drunk and pissed off about being laid off from work and your ex is seeing someone - you have (or easily buy) a gun. Fuck... it's a stupid... sleep on it... can't sleep... get drunk... decide the guy she is with is a dick too. Go to his apt and find 3 ppl, kill them with gun you have. Feel shitty. Shoot yourself in head.
A gun makes mass violence easier, accept it. Some dickhead with a knife can cause a lot of damage - I know - someone I know was stabbed 2 weeks ago in a stupid argument (over a girl

) but no gun was involved. Now, the guy in question actually
has a gun... but it is in a safe and legally owned... not on call for hot headed arguments. He is pressing criminal charges btw.