A Long Island detective shot a man in his home after he charged at investigators with a knife on Saturday, police said.

Nassau County police detectives went to the man’s Copiague house to interview him about a previous incident, but one of the cops shot him as he threatened them charged with a knife at about 4:30 p.m., police said.

The 39-year-old man, who has not been identified by law enforcement, was transported to a local hospital with serious but non-life-threatening injuries, Suffolk County police said.

Copiague is in Suffolk, but police from neighboring Nassau visited the unnamed man as part of the investigation into an incident that happened in their jurisdiction on a previous date.

No other information on the incident was made available.

Suffolk County’s Homicide Squad is investigating.