Combine results of IF statement?

Hello,

I am trying to create a formula on my table to combine the names of the volunteers that are on the same shift each day. I am not sure if i use the IF statement or need to use a lookup?

Here is an example:
If "Date","Location","Start Time","Stop Time" are the same then give all volunteers names with the same criteria. Answer I am looking for outlined in RED.

Thanks for your help!

Nick