Alex already knew. He knew from the way the police stood there, awkward and unhappy. But he also knew from the tones of their voices. Funeral voices… (1.9)
It seems like Alex knows what happened before they even tell him. Of course, Alex has already experienced death before, having lost his parents just weeks after his birth
He had never known his own parents. They had both died in another accident, this one a plane crash, a few weeks after he had been born. (1.13)
Alex's life has been defined by death. We don't want to sound like conspiracy theorists, but there's no way this is a coincidence.
It was almost impossible to imagine that he would never again see the man, hear his laughter, or twist his arm to get help with his science homework. (1.13)
We tend to focus on the little things after the death of a loved one—those are the things we took for granted when they were alive and didn't appreciate at the time.
Alex killed a couple of hours knocking a few balls around on his uncle's snooker table—and then felt vaguely guilty when Jack caught him at it. But what else was he to do? (1.33)
Is there a proper way to handle grief? Alex tries to distract himself from his unsettling reality, even though doing so makes him feel guilty.
He glanced at the slices of cold lamb on his plate. Dead meat. Suddenly he knew how it felt. (4.97)
First, we've got to give Alex some props—his quippy one-liner game is off the charts. But this is an important moment, because it's the first time Alex has to face the possibility of his own death.
"That's not our problem, Mrs. Jones. If the boy gets himself killed, at least it will be the final proof that there is something wrong. […] In a way, it would almost help us if he was killed." (6.19)
Mr. Blunt has a detached relationship with death. Sure, it might seem a bit gross, but it's just how he deals with facing death on a daily basis.
Her breath always smelled faintly of mint. As head of Special Operations, how many men had she sent to their deaths? […] Perhaps it was easier for her if her breath was sweet. (6.83)
Mrs. Jones isn't as bad as Mr. Blunt—at least she tries to soften the blow. This is one of a handful of hints that Mrs. Jones is more empathetic than her blunt buddy.
"And stay there. I would be inconsolable if you were accidentally shot and killed in the darkness. Although, of course, it would save me four thousand pounds." (9.65)
Keep in mind that Sayle thinks Alex is just a contest winner when he says this to him. That's one bad dude.
For a few seconds he looked up at the moon as if trying to admire it one last time. Then the black water folded over him. (9.95)
This is, as far as we can tell, the first time that Alex actually witnesses someone dying. It's a turning point, both for the plot and for Alex's character development.
Again his imagination got the better of him. He could see himself, pinned underneath the rock in the freezing blackness. He couldn't imagine a worse way to die. (11.57)
Despite the many firefights that Alex partakes in, he's never more terrified of dying than when he is alone in a deep, dark cave.