Mexico’s ambassador to the United States detailed last week how the administration of President Barack Obama left his government in the dark while arming violent drug cartel criminals through Operation Fast and Furious.

Last Thursday, Mexican ambassador to the U.S. Arturo Sarukhan told a forum on Capitol Hill that the Obama administration’s handling of the operation demonstrated an “outstanding lack of understanding of how criminal organizations are operating on both sides of our common borders.”

The operation led to the killing of hundreds of Sarukhan’s fellow citizens and two American law enforcement agents: Border Patrol agent Brian Terry and Immigration and Customs Enforcement agent Jaime Zapata. The identities of the countless Mexican victims are unknown.

“Mexico was never apprised how the operation would be designed and implemented,” Sarukhan said on Thursday at a left-wing event hosted by the New Democrat Network and the New Policy Institute.

“Regardless of whether this was or was not the intent or the design of Fast and Furious, the thinking that you can let guns walk across the border and maintain operational control of those weapons is really an outstanding lack of understanding of how these criminal organizations are operating on both sides of our common borders,” Sarukhan said, adding that he thinks the Obama administration had significantly damaged its popularity in Mexico.

The revelation that Mexico was kept in the dark as the Obama administration pumped thousands of weapons into the hands of criminals in its country – criminals who then used the weapons to kill people – comes after news broke that President Barack Obama thinks it’s part of his job as president to kill people, as detailed in a soon-to-be-released book by Newsweek investigative reporter Daniel Klaidman.

According to excerpts from Klaidman’s book, “Kill or Capture,” former President George W. Bush’s counter-terrorism adviser Richard Clarke told Obama early in his presidency that the job required he get his hands dirty.

“As president, you kill people,” Clarke told Obama, according to the book.

Klaidman writes that Obama was unshaken by that remark.

“An inscrutable Obama looked back at Clarke, not betraying any emotion. ‘I know that,’ Obama told Clarke in an even tone,” the book excerpt reads. “‘He didn’t flinch,’ Clarke later said of the meeting.”

In Fast and Furious, the administration likely knew people would die because its actions. The Obama administration’s Bureau of Alcohol, Tobacco, Firearms and Explosives facilitated the sale of the weapons to straw purchasers, who then trafficked them into Mexico. The overall plan was to “track” trafficked weapons to where they ultimately ended up, allowing law enforcement to target bigger kingpin criminals in the weapons trafficking trade.

But the only way to “track” those weapons after they were “walked” into Mexico was to find them at stings or crime scenes. When Mexican drug cartel operatives kill people, they often ditch their weapons at or near the crime scenes.

Agent Terry’s murder on Dec. 15, 2010 sparked a national outcry and what has become a lengthy congressional investigation that’s lasted more than a year. Despite a series of hearings, document requests and congressional subpoenas, Attorney General Eric Holder and the Obama administration have failed to provide complete answers about Operation Fast and Furious – which has turned the issue into Obama’s bloodiest scandal.

NEXT PAGE: Eric Holder had to be talked out of “depression” >>

The investigation has discovered that Holder himself received a series of briefing documents explaining Fast and Furious and the gunwalking tactics it employed, even though he now claims he didn’t read the memos. Since the investigation began, 129 congressmen, three U.S. senators, two sitting governors and presumptive GOP presidential candidate Mitt Romney have all demanded Holder’s resignation.

In addition to failing to hold Holder accountable for Fast and Furious, Obama has not held any other officials involved accountable. The U.S. Attorney for Arizona, Dennis Burke, has resigned, but nobody in the administration has said he quit because of Fast and Furious.

The administration promoted now-former acting ATF director Ken Melson into Department of Justice leadership, too, essentially rewarding him for his role in the scandal.

As Klaidman also reveals in his book, Obama’s senior adviser Valerie Jarrett has backed up Holder in the past and dissuaded him from resigning. Politico’s Mike Allen reported on Saturday that Klaidman details in his book that Holder planned to quit in fall 2010 amid the Khalid Sheikh Mohammed controversy after sinking into a “depression,” but Jarrett talked him out of it.

“The loss of his mother, the continuing criticism over KSM, the lashings in the press, and Holder’s sense of isolation within the administration had turned his job into a grind,” Klaidman wrote, according to excerpts given to Allen. “He woke up on many mornings with a knot in his stomach, not sure if he’s be able to make it through the day. He told [his wife] Sharon [Malone] he didn’t know if he had the emotional strength to go on as attorney general. He thought seriously about returning to his Washington law firm.”

Klaidman says it was Jarrett who talked Holder into staying because she thought it was what was best for Obama.

“Few people could talk to Holder as directly as Jarrett could,” Klaidman wrote. “She started by gently telling him, ‘You’re my friend and I care about you…. This will not be good for you and it will not be good for your friend, the president.’”

“Jarrett didn’t elaborate, but she didn’t have to. Holder understood that if he quit barely two years into Obama’s first term, it would be widely assumed that he was either driven out by Tammany Hall or that he’d quit because he was disillusioned with the administration’s refusal to back him up,” Klaidman continued. “His exit would have become a rallying cry for the liberal base of the party, and it would damage Obama politically just as the midterm elections were looming. He had to stay.”

It’s unclear at this time, though, whether Jarrett still has Holder’s back.

Follow Matthew on Twitter