Just to clarify, we figured out what it was.
When his Blockland froze, he was chatting to me and said "I need to know whats the matreiald" in response to something I said.
Then he proceeded to respond to something else that contained an "o" in it and that's what saved to the Blockland chat.
He also must've used Ctrl at some point and when he hit K to say something it killed him.
"I need to know whats the matreiald"
"I need to know whats the matreiald"
"he matreiald"