There are two extremely good reasons for there to be a trial, well 4 if you count the normal reasons the CPS apply in the UK as well as the two dead guys...
Nope, that isn't necessarily a good reason to push ahead with 1st-degree homicide charges! The firearms charge, sure. We don't automatically carry on and go to trial in the UK simply because people have died (see cases where burglars have been killed etc..), the police will initially charge and interview under caution of course but that doesn't need to go any further - obvs people don't often carry loaded firearms, in public, in the UK though.
The getting locked up after being charged is entirely normal for the US justice system, as is the huge bail amounts when you've got someone who went out with a gun and ended up killing people
Nah that's dubious, there are people locked up and released on bail frequently in the US including for shooting-related incidents that fall short of murder - bail set at 2 million is unusual, 1st degree murder can typically be up to 1 million (or just denied) other felonies start at around 50k or so according to what I've seen so far. Note these aren't murder charges but homicide charges, they're supposed to take into account age, prior convictions/felonies, chance of reoffending etc..etc..
regardless of the what the defence claims happened
Nothing about what the defence claimed to have happened, as mentioned in court this isn't a who done it... the facts are pretty much established, the arguments are over whether it was a reasonable use of force etc.. +. some convoluted argument the defence will try re: the underage firearms charge.