Here "blood" represents a person's death. To be responsible for their own death is spoken of as if their blood would be on their heads. Alternate translation: "their death will be their own fault" (See: [[rc://en/ta/man/translate/figs-metonymy]] and [[rc://en/ta/man/translate/figs-metaphor]])
Here "a hand is laid upon" is a polite way of referring to causing someone injury. Alternate translation: "if we cause injury to any" (See: [[rc://en/ta/man/translate/figs-euphemism]])