One of the differences between people who don't own guns, and thus don't carry them, and people who do own guns, and carry them (or keep them nearby) is that people who don't have guns nearby can't grab them when they get angry about something petty.
Suspect, 19, arrested after deadly shooting at Starbucks drive-thru in Lake Worth Beach
So, here's the basics. The suspect apparently cut off the victim in the drive-thru line at the Starbucks. The victim apparently went road raging in the parking lot, and assaulted the suspect's car, where the suspect, his girlfriend, and their baby were located. As the victim went back to his car, the suspect got out and reportedly shot the victim three times. He died later at the hospital.
There's a couple of lessons here.
One, even though other people are inconsiderate jerks, is it really worth going ape-shit because you got cut off in the drive-thru line and have to wait three more minutes for your cafe mocha?
Two, given that American leads the world in gun ownership, one must assume the possibility that the person who you are considering confronting/assaulting might have a gun, and might be tempted to use it on you. Is it worth your life to take the chance to make a point, particularly in a violent manner?
Three, it's never a good idea to assault someone's car when there's a baby inside (usually with a parent inside too). This induces protective reactions.
Four, I expect that though the suspect will go to jail (which isn't worth it at all), that he'll be able to get the crime of which he's accused (murder) reduced to something like aggravated manslaughter, because the victim clearly did come after him for being an inconsiderate jerk. It wasn't premeditated.
Five, don't carry a Glock in your car if you can't control your temptation to use it in non life-threatening situations. And if you do use it, maybe you should shoot at the other guy's car and not at him.