Liverpool manager Jurgen Klopp says he feared for his former Borussia Dortmund players' safety after the bomb attack on their team bus.
Three explosions went off as the Dortmund team made their way to their Signal Iduna Park stadium for the Champions League quarter-final first leg against Monaco on Tuesday.
Klopp spent seven years as the German club's manager, signing many of Dortmund's current players, and as soon as he heard news of the attack he feared the worst.
The German tried to contact his old team and was relieved when it emerged there were no fatalities, with Dortmund defender Marc Bartra needing surgery on a wrist injury as a result of the attack.
"Everyone can imagine it was a really difficult moment for me," Klopp said on Thursday.
"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."
Dortmund manager Thomas Tuchel has criticised UEFA, European football's governing body, for disregarding the feelings of his squad by rescheduling the first leg to kick off less than 24 hours after the incident in Germany.
Tuchel claims the club were informed of the decision by text message and Bartra was still in hospital while his team-mates were losing the first leg 3-2 to Monaco.
Klopp agrees with Tuchel that UEFA underestimated the mental scars inflicted on the Dortmund players by such a traumatic experience.
"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," he said.
"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."
The German Federal Prosecutor's Office said three letters claiming responsibility found near the site of the attack made Islamic extremists the possible perpetrators.
Security has been increased at Premier League grounds this season in the wake of terrorist attacks at sporting and non-sporting events around Europe, but Klopp said he had no specific concerns about the safety of himself or his players.
"All of us do everything we can do. Obviously there are a few people (terrorists) around who have new ideas and can you be prepared for that?" he said.
"Am I concerned? No. But in all parts of life we can only give 100 per cent and I'm sure everyone is doing this to give you the best security you can have."