There might be more hairsplitting in legalise, but colloquially, it means the same . . .
Actually, U.S. law generally recognizes a spectrum that ranges from premeditated killings (maximum culpability), unpremeditated but intentional killings, unintentional killings in the course of the commission of another felony ("felony murder"), unintentional killings under other circumstances explicitly defined by statute to produce criminal liability, and killings that do not produce criminal liability but may produce civil liability.
Only the last of these could be described as genuinely accidental. If a rented house has an unsafe condition that the landlord knew or should have known could cause an injury to a tenant, and the tenant is killed as a result of that unsafe condition, that really is an accident and the landlord is not guilty of a crime. However, the tenant's survivors may be able recover damages from the landlord for causing the tenant's wrongful death.
The police officer in Minnesota was initially charged with "third-degree murder" under a somewhat unusual statutory provision in that state:
Whoever, without intent to effect the death of any person, causes the death of another by perpetrating an act eminently dangerous to others and evincing a depraved mind, without regard for human life, is guilty of murder in the third degree . . .
Subsequently, the charge was amended to felony-murder:
Whoever . . . causes the death of a human being, without intent to effect the death of any person, while committing or attempting to commit a felony offense . . . [shall be guilty of second-degree murder]
I understand why you might have concluded that, colloquially, "unintentional" is equivalent to "accidental," but the distinction is clear, and fundamental to the determination of whether someone has committed a crime―and the political as well as legal issue here is
criminal misconduct by the police.