Hello and welcome to HCM.
As an Urologist
, i can fully understand your anxiety.
The blood in semen called hemo/hemato-spermia, isn't due to vasectomy.
Common causes are prostate enlargement,it's cancer and prostatitis
1.He'll need to get examined by an Urologist, and get certain tests like,
2.Urine routine and culture.
,RBS,PSA,platelets and LFT.
scan-KUB and TRUS.(trans rectal scan).
According to the reports,proper treatment can be advised.
For my expert opinion on any doubt,send it as a direct question, to me.
Dr.Matthew J. Mangat.