A former United Nations missile inspector said Monday that North Korea's intercontinental ballistic missile reentry vehicle "did not survive" last week's test, meaning the hermit regime needs more tests.

Video captured from a rooftop camera in Japan appears to show North Korea's Hwasong-14 ICBM reentering the atmosphere, then breaking up and destroying the reentry vehicle.

"You see small bright radiant objects that are shedding off the reentry vehicle — and then it suddenly begins to turn very dim," Michael Elleman, a 38 North think-tank analyst and consulting senior fellow for missile defense at the International Institute for Strategic Studies, told reporters in a conference call Monday. "That should not occur. Most likely it broke up into pieces."

On Friday, North Korea test-fired its Hwasong-14 missile, which flew about 45 minutes and splashed down off the northern coast of Japan. A rooftop camera operated by Japan's public broadcaster, NHK, appeared to have captured the missile's descent back to earth — and it shows what Elleman said is convincing proof of the reentry failure.

Pyongyang's first known launch of the long-range ballistic missile took place on July 4, but it's still unclear if that test survived the reentry phase. However, the Friday launch led to video of a critical stage of an ICBM missile's return to earth when the heat and stress on the weapon would be the greatest.

"In short, a reasonable conclusion based on the video evidence is that the Hwasong-14 reentry vehicle did not survive during hits second test," Elleman wrote on 38 North blog Monday. "If this assessment accurately reflects reality, North Korea's engineers have yet to master reentry technologies and more work remains before Kim Jong Un has an ICBM capable of striking the American mainland."

Similarly, Elleman said that if a nuclear device had been on the missile, then it probably wouldn't have survived the full journey. Elleman's past experience includes serving as a United Nations commission weapons inspector in Iraq, and a scientist at U.S. defense contractor Lockheed Martin (NYSE: LMT) as well as government services giant Booz Allen Hamilton (NYSE: BAH) in programs working with the Pentagon, among others.

"If the bomb itself were exposed to these very severe conditions, it would be torn apart," said Elleman. "In short, if the reentry vehicle breaks up, the bomb is not going to be useful — and it's not going to detonate."