Two Goblins, One Square: Shock Trooper Feat - Domino Rush questions

[Mars Ultor]

Last night was the first time my character used the Shock Trooper: Domino Rush feat and it raised some questions. The feat says that you can Bull Rush one creature into another creature's space, and that allows you to "make a free trip attempt against both foes at the same time."

The "at the same time" part led us to believe that one roll applied to both opponents. But then we were unsure as whether an initial touch attack to trip was necessary.

We're not sure the sequence of events: First my character makes an (Improved) Bull Rush against a foe, then there's a Strength check us to see if I'm successful and push him back. If I'm successful and push it into an adjacent square where another foe is standing, then I get my free trip attempt against them both.

Is it necessary for me to make a single touch attack which is resolved independently against each foe? Or is that already resolved because I forced two creatures into one square?

Or, after the Strength check to determine if the Bull Rush was successful, do we move immediately to the character making a single Trip Strength check which is applied independently against both foes?

[Hackulator]

I believe you have to make 2 separate rolls for the trip. This is the general rule and in situations where one attack roll affects 2 enemies it almost always says this. "At the same time" just means both attacks go off at the same moment. Unfortunately "trip attempt" is not super well defined but probably you need to make both the touch attack and the strength check by RAW.