Dried blood on carpet.

wet, blot,wet,blot ?Cold water only .

White wine vinegar and bicarbonate brought red wine off a cream carpet for me. so it should work on blood.

I use Vanish gold on vomit and blood stains - the carpet one usually does the job.

It's a common problem in our house. I've found that fancy cleaning products don't really do the job. If there's a lot of blood etc., I leave it to dry and then use a stiff brush to remove as much as possible. That way there isn't much left that can spread when it gets wet. After that it's usually water and disinfectant.

Put a rug over the top?

I would use just water and repeat until it came out.

Cold water works fine on small stains but if that doesn't get it cleaned I'd try dabbing a bit of milk on to clean it. Blood needs cold water, even ice cubes will do it usually but you could try salt or baking powder if those don't lift the stain. If it's your neighbours carpet I'd not even try , just clear up the messy remains and let them do it themselves.

For blood Ace gentle bleach. It doesn’t bleach the colour out but test on an inconspicuous area first.