WASHINGTON » A U.S. aerial gunship attack on a hospital in Afghanistan that killed 42 people occurred because of human errors, process mistakes and equipment failures, and none of the aircrew or U.S. ground troops knew the target was a hospital, a top U.S. general said today.

“This was an extreme situation” complicated by combat fatigue among U.S. special operations forces, Gen. Joseph Votel told a Pentagon news conference. Votel headed U.S. Special Operations Command at the time of the tragic attack last fall. In March he took over U.S. Central Command, which oversees military operations in Afghanistan and the Middle East.

Sixteen military members have been disciplined for their roles in the tragedy, Votel said. None face criminal charges.

Doctors Without Borders, the international charity organization whose hospital was destroyed in the attack, said in a statement today that it would like to see an “independent and impartial” investigation. It said the punishments announced by the U.S. military are inadequate and “out of proportion” to the deaths, injuries and destruction caused by the mistaken attack.

“The lack of meaningful accountability sends a worrying signal to warring parties, and is unlikely to act as a deterrent against future violations of the rules of war,” the organization said.

Votel said investigators concluded that certain personnel failed to comply with the rules of engagement and the law of armed conflict, but that those failures did not amount to a war crime, he said.

“The label ‘war crimes’ is typically reserved for intentional acts — intentional targeting (of) civilians or intentionally targeting protected objects or locations,” Votel said. “Again, the investigation found that the incident resulted from a combination of unintentional human errors, process errors and equipment failures, and that none of the personnel knew they were striking a hospital.”

Meinie Nicolai, president of Doctors Without Borders, also known by its French initials MSF, took issue with Votel’s assertion.

“The threshold that must be crossed for this deadly incident to amount to a grave breach of international humanitarian law is not whether it was intentional or not,” Nicolai said, noting that with various countries fighting in the region with different rules, “armed groups cannot escape their responsibilities on the battlefield simply by ruling out the intent to attack a protected structure such as a hospital.”

Votel expressed “deepest condolences” to those injured and to the families of those killed and said compensation payment was made to victims’ families.

Zabihullah Neyazi, a nurse who lost his left arm, eye and a finger in the attack, said administrative punishment wasn’t enough and that a “trial should be in Afghanistan, in our presence, in the presence of the victims’ families, so they would be satisfied.”

Votel said the trauma center was on a U.S. military no-strike list but that the gunship crew didn’t have access to the list because it launched its mission on short notice and did not have the data loaded into its onboard systems. He said the military has sought to avoid similar mistakes in the future by requiring that such data be pre-loaded into aircraft.

The Pentagon today released a memorandum from Defense Secretary Ash Carter ordering military commanders to take a series of steps over the next four months to “mitigate the potential for similar incidents in the future.” Among other things, Carter ordered that the Kunduz scenario be incorporated into pre-deployment training as an example of the kind of complicated situations that troops may face in Afghanistan or other war zones.

Central Command released a redacted version of the full investigation report today, including details about what exactly led a U.S. AC-130 gunship to bomb the hospital and how those mistakes were made.

“The investigation determined that all members of both the ground force and the AC-130 air crew were unaware that the aircraft was firing on a medical facility throughout the engagement,” Votel said. “The investigation ultimately concluded that this tragic incident was caused by a combination of human errors, compounded by process and equipment failures.”

Votel said none of the names of the 16 disciplined personnel will be released to protect the privacy of the individuals and in some cases because they are still assigned to sensitive or overseas positions.

According to one senior U.S. official, a two-star general was among them.

A number of those punished are U.S. special operations forces. Some were given letters of reprimand and admonishment; one officer was removed from command; some were suspended from their duties and some were given extensive retraining. No one was sent to court-martial.

“It is important to point out that these adverse administrative actions can carry severe repercussions on the careers and professional qualification of these individuals,” Votel said, to include possible denial of promotion or advancement and possible removal from the service.

The crew of the AC-130, which is armed with side-firing cannons and guns, had been dispatched to hit a Taliban command center in a building 450 yards from the hospital, the U.S. military said in November. Hampered by problems with their targeting sensors, the crew relied on a physical description that led them to begin firing at the hospital even though they saw no hostile activity there. Votel today confirmed that no hostile firing was seen there.

A separate U.S. report on the incident, obtained last fall by the AP, said the AC-130 aircraft fired 211 shells at the hospital compound over 29 minutes before commanders realized the mistake and ordered a halt.

Associated Press writers Deb Riechmann in Washington and Rahim Faiez in Kabul contributed to this report.