A suspected drunk driver struck and killed an off-duty police officer on a motorcycle early yesterday morning in Inwood.

Police said Officer Alexander Felix, 31, was traveling southbound on Dongan Place and Broadway when Kevin Casado, 32, traveling northbound in a white minivan, hit him head-on. Felix was pronounced dead at the scene. Mr. Casado was taken to Harlem Hospital, where he was arrested for driving while intoxicated, vehicular manslaughter, reckless driving, and reckless endangerment.

The police commissioner, Raymond Kelly, said Felix was a “fine young man” and called the accident “a terrible tragedy.” Felix was a former auxiliary officer who had served on the police force in Harlem for three years.

Mr. Casado’s blood-alcohol level was “significant” at the time of the accident, Mr. Kelly said.

Yesterday, friends and family gathered at the apartment Felix shared with his girlfriend, who is eight months pregnant with their first child.

Felix was always happy and smiling, his best friend, Jason Regalado, 29, said. “It seemed like this guy never had a bad day,” he added.

Acquaintances of Mr. Casado, an elevator operator and father of three young children, said he is a hard-working and devoted family man. His sister, Margie Casado, 29, said her brother did not mean to hurt anyone. “I know it wasn’t intentional,” she said. “We feel so sorry for the loss.” The police department will set up more drunk driving checkpoints around the Fourth of July this year, Mr. Kelly said.