... training exercise at a Washington D.C. library, authorities said.
According to a Friday statement from the Metropolitan Police,
, 58, a former lieutenant with
the Metropolitan Police Department
, was arrested after 25-year-old
, of Indian Head, Maryland, was killed.
He is accused of involuntary manslaughter.
was working for a private contractor that was training police who work for the library system when the incident happened Thursday afternoon, police said.