The major cause of coughing up blood is chronic bronchitis or bronchiectasis. Other possible
causes of coughing up
blood include COPD, lung cancer, tuberculosis, pulmonary embolism, pneumonia and lung abscess to name a few. Also, check to see if he is on blood thinners for heart disease, this could be causing the bleeding. I suggest he should go the ER, for immediate evaluation.
Hope this helped and do keep us posted.