Massachusetts State Police are investigating after a man reportedly fired a gun outside the Massachusetts Correctional Institution in Shirley on 24 December. Corrections officers at the medium-security prison reportedly heard a single gunshot outside at around 3.25pm EST (8.25pm GMT).

Officials with Massachusetts State Police said the shot was fired in the vicinity of Harvard Avenue, MassLive reported. Police increased security around the prison after an armed white man was allegedly seen fleeing the scene on foot. The man was described as wearing dark-coloured trousers.

Police officials said the prison was placed on lockdown due to standard operating procedure, CBS Boston reported. All inmates were accounted for and there were no reported injuries. The prison, which is located about 42 miles northwest of Boston and has 13 inmate housing units, is home to convicted murderer and former New England Patriots tight end Aaron Hernandez.

Police said that aerial and K-9 units, which conducted a search of the immediate area out to State Road near Route 2, were unable to find the suspect. "MSP patrols in the area will remain on alert for the potential suspect," police later said. Authorities have not ruled out the possibility that the man was a hunter.

According to CBS Boston, Shirley Police received a report around 7.15pm/12.15am of an attempted house break-in by a man in the area around the prison. However, State Police said they are unsure if the two incidents are related.