Simple enough. Whenever an Engineer's building is destroyed by another player, it is printed to the console. This is meant to imitate the standard notifications of a player's death.
Code:
Cannon Fodder killed IvanTheSpaceBiker with reserve_shooter.
The Administrator killed THEM with scattergun.
Mindless Electrons killed SomeDude's sentry with minigun.
Mindless Electrons killed SomeDude's dispenser with minigun.
Mindless Electrons killed SomeDude's teleporter with minigun.
SomeDude killed Mindless Electrons with pomson.
Source is attached, and can also be found
here.