grammatical number - Should you use “it” or “they” when referencing a group of people?

Should you use it or they when referencing a group of people?

Here is the example sentence:

A group of students was walking on the road when a truck hit them/it and it/they was/were immediately admitted to hospital.

Could native speakers and grammarians please answer this question? For me, it should be used because I am taking about the group as whole, and the group is one thing not many things.