A team member just had it and I was able to spec:
He pulled off some serious clutch play as Proxy when planting in the very last second. I am sure he got it down in time. Planting Siren goes off. Then he got a fast kill. All within very maybe 2sec max.
There was still a player alive on each team and we now lost the round in the next few moments. Likely due to time up but I dont remember the message anymore.
Next round he spawned again as proxy with the bomb. He was not able to do anything but chat with us.