It all took place last week.
A 44-year-old man has died in hospital following an incident in Holbrook Street, Heanor.
Officers were called to reports of a disturbance at an address at around 12.30am on, Tuesday, 19 November.
At the scene officers found Mark Pierce unconscious, along with another man, aged 26, who suffered a head injury after allegedly being struck with a baseball bat.
Mr Pierce was taken to Queens Medical Centre where he died on Wednesday, 20 November.
Our thoughts are with his family and friends at this time and they are receiving support from specialist officers.
Two men, aged 59 and 26, both from Heanor, have been arrested and bailed in connection with the incident.
The incident has been referred to the IOPC by the force.