Do people know that birthdays can kill him?

Yes, as long as you know his birthday, and then write it on a piece of yellow paper, you must write it in cinnabar (cinnabar drugstore can buy it). You put yellow paper under the insoles of your shoes and walk 30,000 steps every day for 7749 days (you can't change shoes and wash insoles during this period). Then you take out the yellow paper and send it to him anonymously when it expires. See if he will die.