A prominent Long Island cardiologist vanished last month after parking his BMW at a Nassau County train station, police said Tuesday.

Dr. Randy P. Kiewe, the founder of CompleteCare Cardiology in Lake Success, is a married father of teenage daughters who has battled depression in the past, according to sources.

The final sighting of Kiewe, 47, came at 6:30 a.m. Sept. 22 at the Roslyn Long Island Rail Road station.

Nassau County cops put out a Silver Alert for Kiewe, who was named a top cardiologist by the Long Island Press.

“It’s an active investigation,” said Officer Steve Zacchia, a police spokesman.

A woman who answered the door Monday at Kiewe’s home in the affluent town of East Hills would not comment.

“It’s so sad and tragic for everybody,” said a neighbor.

At his office, patients are being referred to other doctors, as the staff waits and posts sad messages on the practice’s Web site about remaining “optimistic.”