My Son Is In The Military, As Far As He

My son is in the Military, as far as he knows pretty healthy, 22 years old. He just started having high blood pressure, out of nowhere. They did blood work to check for a few things. The blood work checked out fine for whatever they were checking for. He was put on a blood pressure medication which he has been taking for 2 weeks. Today while at Physical Therapy, after surgery for ACL repair, they had him walking on a tread mill and his heart rate was 163. He went to a walk in clinic. When they checked his blood pressure and heart rate, they were both good. What could be going on with him having high blood pressure out of nowhere and now a pulse rate of 163 just walking on a tread mill? He is only 22 years old