Old Tech is more direct.
I presume that the campus has a fire alarm system, something nice and low tech like bells / flashing lights / audible warnings via tannoy, unless they also send e-mails out with the title "You're on Fire!"
From the news reports some of the students were killed in a French lesson, so I think that they weren't watching their inboxes at the time. There might also be a problem with the mobile phone alert as some Professors have a strict 'turn phones off policy' - there's a bunch of YouTube vids of kids having their phones taken off them and smashed, in at least one case.
A simple alert system might have saved some lives, but the reports say the shooter locked and chained shut some of the exit doors, so maybe having dozens of kids loose in the corridors might have lead to more deaths.
There's no simple solution, other than actually having some form of policy that seems rational and logical then putting it into practice. It seems none of that applied in this case.