The new chief constable of the West Mercia police in England said she was "deeply sorry" for the 2016 use of a stun gun that led to the death of former professional soccer player Dalian Atkinson.

Five years ago, Atkinson, a former striker for Premier League team Aston Villa, was arrested in Telford, outside the central English city of Birmingham.

The BBC reported that Atkinson had been suffering from an illness that affected his physical and mental health and was dealing with a mental health crisis when he was arrested. Neighbors said Atkinson was yelling that he was the Messiah outside of his father's house.

Constable Benjamin Monk responded by using his stun gun against the 48-year-old for 33 seconds, over six times longer than customary. He also kicked Atkinson in the head twice, hard enough for his boots to leave an impression on Atkinson's face.

Atkinson died in a hospital shortly after. In June, Monk was convicted of manslaughter and sentenced to eight years in prison.

Pippa Mills, who started as the West Mercia police chief in September, wrote an apology letter to Atkinson's family.

According to the BBC, she mentioned in the letter that she and the police force had an "obligation" under the European Convention on Human Rights to "acknowledge and accept" that Atkinson's human rights were breached when he was killed, adding that Monk's actions were "in direct contradiction" with the police force's standards.

"A police uniform does not grant officers immunity to behave unlawfully or to abuse their powers," she wrote. "I am deeply sorry for the devastating impact the actions of a West Mercia officer has caused you and I extend my deepest condolences to you all, and Dalian's wider family and friends."

In a statement, Kate Maynard, Atkinson's family's lawyer, called the apology "welcomed and overdue."

"The chief constable's acknowledgement that a police uniform does not grant immunity is especially pertinent in a year that has seen other terrible examples of deadly police violence," Maynard said.

Dalian Atkinson, Aston Villa, England
The new chief of the West Mercia police force apologized for the 2016 police use of a stun gun that resulted in the death of former professional soccer player Dalian Atkinson. Above, Atkinson playing for Aston Villa in 1993.Anton Want/Allsport via Getty Images

The charity Inquest, which supports the bereaved in cases of deaths involving the state, has said that Monk's conviction is believed to be the first time a British police officer has been found guilty of the manslaughter of a Black man.

It is extremely rare for police in Britain to be convicted of manslaughter or murder over deaths in custody or during contact with the public. Maynard said Monk's conviction was the first of a serving officer on a manslaughter charge in connection with their policing duties in over 30 years.

The Associated Press contributed to this report.

Benjamin Monk, England, manslaughter
The new chief constable of the West Mercia police in England said she was "deeply sorry" for the 2016 use of a stun gun that led to the death of former professional soccer player Dalian Atkinson. Police constable Benjamin Monk (above in June) was convicted of manslaughter and sentenced to eight years in prison in June in Atkinson's death.Joe Giddens/PA via AP