A 19 or 20 year old knows full well that this type of "prank" could injure or kill someone - very different from a child with a bottle rocket or slingshot........
It won't stop them from doing it. It surely didn't stop me. You confuse child with adolescent. Children do not have the knowledge or resources to do these things. Adolesents know how and want to try it out.
Again, the punishment should fit the crime. The crime is determined from intent. Application of "terrorism" to this is plain stupid and irresponsible. How does irresponsible behavior on the part of authorities correct irresponsible behaviors of youth? You seem to seek prison terms for anyone who would operate "outside of the box". Engineering students, and later engineers, always operate that way.