>Why are there so many guns in this God-forsaken country?

Surplus arms after World War 2 led to the creation of the gun industry in the US, and thanks to the Second Amendment and the power of the gun lobby, its relationship with the Republican Party, and decades of popular media making them cool, that's a guaranteed untouchable industry.

> Why did they enter the house, instead of waiting for a specially trained team?

What "specially trained team?" That was the specially trained team. They're specially trained to break down doors and shoot people.

Americans get the policing they vote for, and they consistently vote for tacticool cowboys with Punisher tattoos and against... anything less than more of that.

There is probably a relationship between this and the first question.

>Why did the victim have a gun?

Self defense, presumably, as is his Constitutional right.

> What "specially trained team?" That was the specially trained team.

Weren’t they some local cops? In my country there is a handful of police teams specialised in hostage situations and the like. In case of an "active shooting", local cops would typically establish a perimeter until these guys come and handle the situation (without deaths if possible, although they are sharp shooters).