It's been a busy week for former U.S. Surgeon General Richard Carmona.

On Tuesday, Defense Secretary Leon Panetta announced Carmona would head an independent panel overseeing the investigation into the mishandling of the remains of fallen U.S. troops.

On Thursday, Carmona jumped into the Senate race in Arizona. And on Friday, he stepped down from the panel, and the Pentagon blasted him for keeping his campaign plans to himself.

"If he informed the Pentagon of his intentions, it must have been in the equivalent of a quiet whisper because no one who should have heard about it did," a senior Pentagon official told The Hill.

The official called the decision for Carmona to step down an obvious one, and said it was clear he wouldn't be able to run an investigation and a political campaign simultaneously.

"Separate and apart from any legal issues, we wouldn't have agreed to have someone lead such an important effort on the side while running for office. That would have been a non-starter," the official said.

Camona's campaign did not immediately respond to a request for comment.

For the Defense Department to have been unaware that Carmona was considering a Senate plunge would seem to have required a major lapse in communication. Carmona's deliberations were widely reported in the national media, and President Obama was said to have personally called Carmona to encourage him to run.

Democrats for months had been eagerly courting Carmona to run for Senate, considering him their best chance at taking control of the seat that retiring Sen. Jon Kyl (R-Ariz.) is vacating.

The confusion over whether Carmona could pursue both opportunities simultaneously began on Tuesday, when Panetta announced Carmona would lead the panel overseeing the investigation at Delaware's Dover Air Force Base, which has been engulfed in a crisis over revelations that the base's morgue mishandled the remains of troops who died in Iraq and Afghanistan.

In an interview with The Hill on Wednesday, the day before Carmona entered the race, he dismissed concerns about whether serving in a nonpartisan role for the military while running in the Democratic primary for Senate would be politically problematic.

"I don't see any conflict whatsoever. This is an issue that came up long before anybody was talking about me running for any office," Carmona said.

Carmona observed that many people in public leadership positions balance four or five disparate roles at the time time, and said his work on the panel would have no impact on other things going on in his life.

"I'm in Arizona. This happened in Dover, Delaware. The people are over there. I don't even know — I've never met them. There's no connection whatsoever," he said. "I was asked to do this as a service to the country."

But on Friday, the day after he announced his candidacy, Carmona announced in a Veterans Day statement that he was stepping down.

"This important work deserves the full attention of the review panel, without any distractions," he said. "In order to avoid the opportunity for the appearance of partisanship with this important work, I have decided to recuse myself from the panel."

Carmona, a Vietnam veteran who was awarded two Purple Hearts, noted that he has been working with the Defense Department for months to help put the panel together, and will continue supporting the team through the transition.

Panetta spokesman George Little said in a statement that Carmona had notified the Defense Department he was stepping down on Friday morning.

"Secretary Panetta agrees with that decision, and he will name a replacement very soon," Little said.

-- John T. Bennett contributed