Nova Scotia’s police watchdog is investigating after a man died shortly after being arrested in connection with a two-vehicle collision in Pictou County last month.

RCMP and emergency crews responded to the crash on West Branch Road in River John, N.S. on Dec. 16, 2017.

Police say a car driven by a 50-year-old man collided head-on with another car carrying three adults and a child.

Three occupants of the second car weren’t seriously injured, while one female suffered a serious, but non-life-threatening injury.

Police say the driver of the first car required medical treatment and, while being assessed in the ambulance, he was placed under arrest.

Police say the man became agitated and was then handcuffed. Shortly after, he went into medical distress and was pronounced dead at the Aberdeen Hospital in New Glasgow.

The incident has been referred to Nova Scotia’s Serious Incident Response Team, which is responsible for investigating all serious incidents involving police in the province.

SIRT says it is investigating because the man had been placed under arrest for impaired driving prior to his death.