Thermal vision would/could have given them a good idea. Until the fire started. However it started.
would you want to make sure he was arrested, or killed? I'd want him dead as a doornail.
If I get to pick, I'll take quadraplegic going through the automatic death penalty appeals process.
If I don't get to pick that much, I'll still take arrested. I'll get more closure by making the victim statement at trial and then attending his lethal injection, firing squad, or electrocution than watching parts of what MAY have been his death on TV.