Updated

A second top administrator in the Tulsa County Sheriff's Office resigned Tuesday in ongoing fallout from the shooting death of a restrained man by a volunteer deputy who said he mistook his weapon for a stun gun.

The resignation came as results from an autopsy showed that 44-year-old Eric Harris suffered internal bleeding and collapsed lungs after he was shot April 2 by volunteer deputy Robert Bates. Harris' cause of death was a gunshot wound to the right armpit, the Oklahoma medical examiner said in ruling the death a homicide.

The report also found that Harris had methamphetamine in his system when he died.

Bates — a friend of Sheriff Stanley Glanz, who has donated tens of thousands of dollars in cash and equipment to the office — has pleaded not guilty to second-degree manslaughter, saying he confused his stun gun and handgun after Harris ran from police during an undercover sting operation.

Bates resigned his volunteer position in the sheriff's department shortly after the shooting, and his attorney said Tuesday that Bates had canceled his Bahamas vacation after media reports mocked him. During his arraignment in April, a district court judge gave Bates permission to leave the country for one month.

"He was looking forward to the trip with his grandkids," attorney Corbin Brewster told The Associated Press. "He was ridiculed in the national press for sticking to that plan."

Maj. Tom Huckeby's resignation from the Tulsa County Sheriff's Office was to take effect on Aug. 1, said Meredith Baker, an attorney for the office. She said Huckeby was away on vacation and didn't give a reason for his resignation.

"I can't speak to what was in his head," Baker said Tuesday.

Phone numbers listed for Huckeby were either disconnected or rang unanswered, and he did not respond to an email seeking comment.

Huckeby is the father of Michael Huckeby, a sheriff's deputy who was also involved in the sting operation with Bates. A video of the shooting shows the younger Huckeby placing his knee on Harris' head as he lay on the ground after being shot.

Last month, Tim Albin, the second-ranking official in the sheriff's office, resigned after a leaked 2009 internal investigation showed that Albin and Huckeby knew that Bates was inadequately trained but pressured officers in the department to look the other way. The sheriff's office initially denied the existence of the investigative report, which also noted that some reserve deputies were upset over the special treatment Bates was being given by Huckeby and Albin.

On Monday, Maj. Shannon Clark, the sheriff's office chief spokesman, was put on administrative leave with pay, pending a performance evaluation in the wake of the shooting.

Bates is white and Harris was black, but the victim's brother has said he does not believe race played a role in the shooting.

Harris' family and others have previously called for the sheriff's resignation.

A spokeswoman for Harris family attorney Dan Smolen said Tuesday that Smolen has seen the autopsy report but still needed to review its findings independently. Smolen, in a statement, called Huckeby's resignation "a welcome and necessary step."