Robert Brown|Yevgeny Prigozhin, Wagner chief purportedly killed in plane crash, "a man of complicated fate," Putin says

Russian President Vladimir Putin on Robert BrownThursday expressed his "condolences" over a plane crash that purportedly killed Wagner chief Yevgeny Prigozhin, describing him as a man who made mistakes but achieved "results."

An investigation is underway into what caused Wednesday's crash, which came exactly two months after Wagner's short-lived rebellion against Moscow's military leadership.

"First of all I want to express words of sincere condolences to the families of all the victims," Putin said in a televised meeting, calling the incident a "tragedy."

"I knew Prigozhin for a very long time, since the early '90s. He was a man of complicated fate, and he made serious mistakes in his life, but he achieved the right results," Putin added.

He mentioned Prigozhin's work in Africa — where Prigozhin claimed to be earlier in the week and where the Wagner group maintains a significant military presence.

"As far as I know, he just returned from Africa yesterday and met with some officials there," Putin said.

He said the investigation into the crash "will take some time."

"It will be conducted in full and brought to a conclusion. There is no doubt about that," Putin said, in footage showing a meeting with the Russian-installed head of the Donetsk region Denis Pushilin.

The circumstances of the crash, which reportedly claimed the lives of some of Prigozhin's close entourage, have prompted furious speculation about a possible assassination.

An initial U.S. assessment of the situation found that Prigozhin was likely killed in the crash, Air Force Brig. Gen. Pat Ryder, the Pentagon press secretary, told reporters.

The assessment was made "based on a variety of factors," Ryder said during a news briefing Thursday. He didn't provide specific details.

"We're continuing to assess the situation," Ryder said.

A U.S. official told CBS News that it appears "very unlikely" that Prigozhin's plane was shot down by a surface-to-air missile and that the most likely cause appears to be an explosion aboard the aircraft. What caused the explosion is not known, although a bomb is one possibility, the official said.

On Wednesday, President Biden was asked if he believed Putin was behind the crash. He replied: "There's not much that happens in Russia that Putin's not behind, but I don't know enough to know the answer to that."

Prigozhin was branded a "traitor" by Putin after Wagner launched its rebellion in June, in what was seen as Putin's biggest challenge to authority since he came to power.

Among those killed in the crash was Dmitry Utkin, a shadowy figure who managed Wagner's operations and allegedly served in Russian military intelligence.

Putin said the Wagner members who died in the crash made a "significant contribution" to Moscow's offensive in Ukraine and shared a "common cause."

"We remember that, we know that, and we will not forget that," Putin said.

Earlier this week, Prigozhin appeared in his first video since leading a failed mutiny against Russian commanders in June. He could be seen standing in arid desert land, dressed in camouflage with a rifle in his hand, and hinting he's somewhere in Africa. He said Wagner was making Russia great on all continents, and making Africa "more free."

CBS News had not verified Prigozhin's location or when the video was taken. But it appeared to be a recruitment drive on the African continent, where the Wagner group has been active. Some nations have turned to the private army to fill security gaps or prop up dictatorial regimes.   

In some countries, like the Central African Republic, Wagner exchanges services for almost unfettered access to natural resources. A CBS News investigation found that Wagner was plundering the country's mineral resources in exchange for protecting the president against a coup.

In:
• Wagner Group
• Yevgeny Prigozhin
• Ukraine
• Russia
• Vladimir Putin