Groton ― Police arrested a Hartford man in connection with an assault on Monday that left a man with serious head injuries.

Police said they found the victim of the 10:34 a.m. assault, a 46-year-old man, unconscious on the ground in the parking lot at 618 Poquonnock Road, a facility owned by Stonington Behavioral Health Inc.

Police provided first aid to the victim until the arrival of emergency medical personnel from Groton Ambulance, Poquonnock Bridge Fire Department and Yale New Haven paramedics. The victim was taken by ambulance to Lawrence + Memorial Hospital in New London and later airlifted to Yale New Haven Hospital in New Haven for “serious physical injuries to the head,” police said.

Police said they have notified the victim’s family but did not release his name or his condition.

Police said the suspect was taken into custody within an hour of the assault. Antwan T. Strickland, 31, of 47 Orange St. in Hartford is charged with first-degree assault and breach of peace.

Police said Strickland had confronted the victim and struck him, causing him to fall to the ground. Officers found Strickland in front of a neighboring business on Poquonnock Road.

Held on a $750,000 bond, Strickland is due to appear Tuesday in New London Superior Court.

Police said they continue to investigate and ask anyone with information about the assault to contact the Groton Police Department at (860) 441-6712.