【in cold blood】 —said of smth. brutal or cruel done in an unemotional way:

• Sixteen innocent people, make-up artists, technicians and journalists, were murdered 【in cold blood】 in that building.

Note: The expression does not correlate in meaning with the phrase make someone’s blood run cold—(also: make someone’s blood freeze) horrify or shock a person:

• What he saw made his blood run cold. The woman stood there, holding a sword half as long as she was.

【with sang-froid】 —(Fr.) acting calmly and without emotion in a dangerous or difficult situation:

• A man who always acts 【with sang-froid】 has a great advantage over him who is of a lively and easily inflamed nature.