All 3 assassination types are actually achievable on the first level.
- Ballistic
You come equipped with a silenced pistol that you can use (usually in the tutorial part).
- Accident
Make your way to the top deck of the boat and wait by the right life boat until he stands below it.
- Explosive
There is a remote detenator at the begnning of map which you can use when he meets Mr Norfolk and escape through the window.