two stepbrothers (one evil) only survivors of bus crash [s]

[Fiona]

protagonist was a boy, and the story was about how their class was on a
field trip, but the boy needed to use the bathroom. the angry bus driver
pulled over and got frustrated waiting for the boy and sent the boys
stepbrother (also in same class) to hurry him up. The bus driver started
driving away because he was very angry (planning to turn back in 5 minutes)
but the bus crashed down a cliff and the two stepbrothers were the only
survivors.
The stepbrother was a very evil violent kid and they both wandered into an
old army museum where they set up camp for a week. The evil stepbrother
collected all the guns from the museum and warned the brother to stay
upstairs or he would shoot him.
The main character was terrified of the stepbrother and stayed upstairs for
some days during which he tried to escape by climbing down a tree outside,
but was caught by the stepbrother and told to get back inside or he would
shoot him. After about a week a boy who had survived the bus crash stumbled
into the museum and found the two. The new boy from the crash managed to
get upstairs to the protagonist and they had the idea of singing silent
night to the evil boy in order to call a truce(because of a history lesson
they'd had where some soldiers sung the song and the sides at war made
peace)but the evil boy didn't want a truce and shot from the bottom of the
stairs. The protagonist ended up getting shot in the hand and they did
escape somehow by the end of the book.

[Tab]

Fiona, when did you read this book? Remember anything about the cover?

[Fiona]

Sorry forgot to put that in the post, I read it in a school library either 3 or 4 years ago, I think it was suited to ages 11-13 and -frustratingly- I have no idea what it looked like, it was somewhere between 200-300 pages, not a big book

[Kelley]

A Nicer Way to Die by Sam Mills

[Ann aka Iftcan]

A Nicer Way To Die Is the click for Kelley's suggestion.

Fiona--you reviewed this book a year ago (8/11/12) so am I right in saying that this isn't it?

[Fiona]

Yes!! Thank you it was A Nicer Way To Die!!! And yes, I realize I already reviewed it a year ago, I thought I definitely remembered adding it to my to-reads, but at one point I spent ages scrolling through to find it and I couldn't, I must have just scrolled right past it :/