The coach carrying the Dortmund team to Signal Iduna Park was hit by three explosions ahead of the side’s first-leg clash with Monaco in the Champions League quarter-finals, smashing some of the vehicle’s windows and leaving Spanish defender Marc Bartra with an injury to his hand and arm.
Klopp spent seven years at Dortmund, between 2008 and 2015, and led the German side to two back-to-back Bundesliga titles and one DFB-Pokal trophy.
Speaking for the first time after Tuesday night’s attack, the Liverpool boss admitted how “difficult” it has been for him.
"Everyone can imagine it was a really difficult moment for me," he said.
"I don't know how often I have been in that hotel down the years. I know exactly where it is on that road and a lot of my friends were on the bus.
"I tried immediately to get some information. I was really concerned, scared for them [the players], I was scared for everyone.
"I had contact with a few people but I didn't want to bother them with my silly questions so I was waiting like all the rest of the world for more information.”
The German also suggested that the game should not have been rescheduled for the day after the attack but said he “100 per cent understood” why it had gone ahead.
"The last thing I thought about [after hearing the news] was the game but when I watched the game yesterday and I can 100 per cent see both sides [why it went ahead].
"It's really, really difficult to find a date in this really tight schedule but I think everyone would have understood if they said they did not want to play it.
"I was really proud of Dortmund, how they handled it and created this atmosphere.
"The game was not too important but when they played they tried to be at their best.
"But I saw it in the faces of my former players after the game and I saw the shock in their eyes and that was really hard. It will obviously take time to deal with it in a proper way.
"I'm pretty sure if some of the people who made the decision (to play the match) afterwards had been on the bus they would not have played the game but when you are not on the bus you cannot really imagine how it was exactly."
And Klopp urged the football community to move on from the incident and return to normality, despite the distress and concern it has elicited.
“As human beings we all think about this but as long as we are not directly involved, it’s hard but life goes on,” he added.
“I see it like all in the world see it. We have to carry on. We will and we can. We can concentrate on football and training.
“We care about them, we think about them but we have to carry on.”