Derail the train.

Relevant video: https://www.youtube.com/watch?v=-N_RZJUAQY4

While looking for this video i also saw that the same dude made a video 4 years later with the first kids younger sister. She had a slightly different solution: https://www.youtube.com/watch?v=ZULuedsaB9U

There’s another trolley coming, and she’s trying to stop it from running over people again by crashing the first trolley into it.