Cops say it was a domestic incident, but were not more specific.

Law enforcement says Bird is undergoing psych evaluation in a Boston-area hospital.

Cops say Bird is "currently being guarded" at a Boston-area hospital. The victim is being treated at another hospital.

Although details are scarce, the Celtics are clearly concerned, issuing a statement ... "We are aware of the incident involving Jabari Bird and are taking it very seriously. We are actively gathering information and will reserve further comment at this time."

Bird, who was drafted last year, will appear in court Monday, where he will be officially charged.