Long Island philanthropist Gary Melius shot in the head, but why?

He owns a castle and gives generously to charities. He has also donated hundreds of thousands to political candidates and counts a retired US senator as a friend. And he was embroiled in a controversy that led to the downfall of a police commissioner.

On Monday, he was shot in the head by an unknown masked assailant.

Detectives are saying very little about who tried to kill businessman Gary Melius of suburban Long Island in the US state of New York. Officers set up an "informational checkpoint" on a busy road near the crime scene but said little else.

Melius was recovering in hospital and was counting his blessings. "If this near-death experience has done anything it is a reminder to live each day, celebrate life and embrace your family," he said.

Melius, 69, was shot as he got into his car at Oheka Castle, a mansion-turned-wedding palace in Huntington where the businessman and his wife live. Police said the shooter was wearing a mask and said nothing before opening fire.

Built to resemble a French chateau, the 127-room Oheka Castle was one of America's largest private homes when built for German-born financier Otto Hermann Kahn in 1919.