awkook's method is better done just using an invisible
func_breakable (e.g. covered entirely in NULL texture), or completely replaced by a
gibshooter, as it's only there to spawn gibs.
Either way, for the first step you'll use the func_train as both UrbaNebula and awkook already suggested (for how to use it, check the entity guide page UrbaNebula already linked). This will make a brush that moves any path you define for it (such as straight down in your case) and rest at the end.
If this is all you need, then no more is needed to be done.
Any step after that is for creating any secondary effects, for example the brush breaking into pieces when it hits the scientist (this is what awkook was explaining). If you wish to do this, there's at least 3 ways to trigger the effects:
- Timed from when the brush starts falling
- Using the Fire On Pass (message) key of a carefully placed path_corner
- Have the scientist trigger it using its Take Damage TriggerCondition
For the effects themselves, as I said earlier you could use an invisible func_breakable or a gibshooter to spawn whatever gibs you want (even from the ceiling where the brush starts falling from, to simulate it breaking from/through there). An
env_render targetting the brush can be used to turn it invisible, or a
trigger_relay can KillTarget it to remove it from the game, if you want your brush to "break" on collision. It's up to you to find out exactly
what you want to happen and when.
1 Timed:
When you trigger the brush to start falling, have a delayed trigger for your effects. You can calculate this by measuring the distance between the brush' start position and its position when it collides with the scientist (for example 100 units). If you made it fall with a speed of 800 units/second, then the delay should be distance / speed = time. In this example, 100 / 800 = 0.125 seconds.
2 Fire On Pass:
path_corner has a Fire On Pass key that can be used to trigger something when a func_train, well, passes it. Just place it where the geometric center of the train would be when it collides with the scientist.
3 TriggerCondition:
If the scientist is never going to be hurt in any other way, you can use it's TriggerTarget key set to trigger the effects and TriggerCondition set to Take Damage (
2) and it'll trigger the effects once the train starts hurting it.