Two Long Island congressmen sent a letter to the Federal Bureau of Investigation and the Veterans Affairs Department on Thursday asking them to conduct a thorough inquiry into the suicide of a veteran outside the Northport Veterans Medical Center on Long Island.

The veteran, Peter A. Kaisen, 76, of Islip, shot himself on the Northport campus on Sunday. Two people connected to the hospital who spoke on the condition of anonymity because they were not authorized to discuss his death said that Mr. Kaisen had been turned away from the hospital’s emergency room before he killed himself.

A spokesman for the hospital said on Wednesday that there was “no indication” that Mr. Kaisen had been at the emergency room. It is unclear if any official record was made of a visit by Mr. Kaisen.

Image Representatives Steve Israel, left, a Democrat, and Peter T. King, a Republican.

Representatives Peter T. King, a Republican, and Steve Israel, a Democrat, sent a letter to James B. Comey, the F.B.I. director, and Robert McDonald, the secretary of veterans affairs, calling on the agencies to investigate Mr. Kaisen’s death in a “transparent” manner to assure veterans that mental health problems can and will be addressed at V.A. medical centers.