Sensei, quite an incident. But I'm not clear what happened.
The guy was doing a forward ukemi with his leading right arm, instead of making light contact with the mat on side of his hand - his palm hit the mat, I can only assume he took his full weight on the flat of his hand. It was very bad.
Handy with a sword.
About 40 yrs ago we had a dojo in a large sports complex - we often saw the instructor watching our sword techniques - what we didn't know was, he had actually bought a sword and was showing his students `Karate` defence against the sword - he had memorised the Tenkan movement but had forget to take his arm with him, as his student attacked Shomen, he turned leaving his left arm outstreched - the sword was not controlled and continued to cut towards the mat - the Karate instructer had his left hand cut completey off.
Co-author of `Positive Aikido`