When almost about to begin the bombing run (the PFF flares were noticed going down not far ahead), he glanced out the window and saw a Lancaster very close and heading directly for his aircraft. There was no time to avoid a collision.
I felt a bump but did not know where we were hit. The nose went down and I could not pull it out. Told crew we had been hit. Then we went into a violent spin. Controls seemed stiff, intercom went U/S. I shouted for the crew to bail out. The Bomb-aimer and Flight Engineer went out through the front hatch. The Navigator was having trouble. I released my seat harness to give aid. Was thrown against the roof and knocked unconscious. Woke up in the air, pulled my 'chute, and within 20 seconds landed in a tree about 30 miles east of Mannheim.

The assumption that the other aircraft was the Lancaster from 115 Squadron is based solely on my own analysis of the events of the night.

The first point in inspecting the information gathered on this collision is that there is more than one source which state clearly that both KB775 and PD274 were involved in collisions.

The second point, MI9 Liberation reports from the pilots mention that they were travelling in opposite directions, one states entering the target zone while the other mentions leaving the target zone.

The third point is that the crash sites of these two aircraft are located roughly in a line with each other. One was West and North of the T/A and the other to the East and South of T/A. (exact locations not given although South of Koblenz and East of Mannhiem are within that range though distant). Both aircraft continued on for a period of time after the collision. Two of Witwer's crew had time to attach parachutes and leave by front hatch before the aircraft lost control and the other Lancaster crew had time to completely evacuate their aircraft.

My opinion on this is that there was only one collision involving two aircraft.

A second scenario could have been that there were two mid-air collisions. This would mean four aircraft were involved.
The book "Bomber Command War Diaries" states that only 15 Lancasters were lost on the operation. While the book "Bomber Command Losses" lists 17 Lancasters brought down. Other sources also list 17 aircraft lost on that operation.
That would mean 4 out of 17 aircraft were lost in this way. A high percentage, almost 25%. Then when you subtract the known crash sites from the operation which are located far from the T/A, two aircraft were lost on landings back at bases, three were lost on route, the numbers change to 4 out of 12.
If you take into account of those 12 crews, six crews had survivors and no reports of collisions are mentioned.

So it is more likely that there was only one collision involving these two aircraft.

The cause or the aircraft involved is not important. The loss of the men of KB775 is the tragic point. Their loss shows the dangers of carrying out these operations came not only from enemy action they also include collision, being hit by dropping bombs or incendiaries and weather conditions.
No matter what charts and calculations the Operational Research unit could come up with, the true dangers were known to every airmen.