[Hell-met]

How does that happen Hell-met? Do they have to be directly in the line of fire?

Splash damage from the sentry rockets, I think.
So basically it has to fire at an enemy and then your teammates have to be in the splash damage radius of the rockets when they explode.

actually, no

the sentrygun has to be destroyed right after it launches its rockets

the remaining rockets no longer have a team and will hurt anyone they hit

its like the spectator grenade exploit