"And you can't explain that red substance dripping down from the hatch as being paint from paint pellets"

Espen Goffeng did, and he had chance to look at it, touch it and smell it!

No he didn't. He just said that that's what he thought they were firing. He never said that he had checked it out and found it to be paint. He said "I think they're firing some paintball looking stuff". He says "I think". Not, "I know", or even "I believe". And he doesn't address the actual stuff on the wall, but only what he thinks they're firing. He's making an assumption based on prior information gleaned in a different context. Had he checked it out and found it to be paint, he would have said, "No, it's paint." Or maybe, "I checked it out, and it feels and smells like paint". But he didn't do that.