The bomb that was used by the Saudi-led coalition that killed more than 40 children in Yemen earlier this month was sold in an arms deal that was sanctioned by the US State Department.
Munition experts were able to determine that the weapon used to kill dozens on August 9 was a 500lb laser-guided MK 82 bomb made by Lockheed Martin,CNN reports.
Lockheed Martin is one of the US top defense contractors. Munition experts used a number found on a piece of shrapnel to determine the bomb's origins.
The bomb used was very similar to the one used to bomb a funeral hall in Yemen in October 2016.
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The Saudi coalition claimed that 'incorrect information' led to the strike that killed 155 while wounding hundreds more.
Just earlier that year, in March, a US-supplied precision-guided MK bomb struck a Ymeni market and killed 97 people.
Following the attack at the funeral, President Obama banned the sale of precision-guided military technology to Saudi Arabia, citing 'human rights concerns.'
In March 2017. President Trump's then-Secretary of State Rex Tillerson overturned the ban.
The US was quick to assert that it did not make targeting decisions for the Saudi Coalition that is fighting a rebel insurgency in Yemen.
However, the US does conduct billions in arms deal with the coalition and aids in the refueling of Saudi combat crafts. The two groups also share intelligence.
'I will tell you that we do help them plan what we call, kind of targeting,' claimed US Secretary of Defense James Mattis. 'We do not do dynamic targeting for them.'
The students involved in the latest strike had been out enjoying a day trip when catastrophe hit.
In total, 51 people died in the airstrike while another 79 were wounded. Of the number of those killed, 40 were children, Houthi Health Minister Taha al-Mutawakil said last week. He stated that 56 children were injured.
And according to witnesses near the scene, the bomb made a direct hit for the bus.
'I saw the bomb hit the bus,' one witness claimed. 'It blew it into those shops and threw the bodies clear to the other side of those buildings. We found bodies scattered everywhere, there was a severed head inside the bomb crater. When we found that, that was when I started running. I was so afraid.'
So many of the bodies were so badly mutilated that identification for them proved to be impossible.
A single backpack, schoolbooks, shoes and warped metal were all that was left in the destruction.
When asked about the bomb's and their origins, coalition spokesman Colonel Turki al-Maliki said: 'The democratically elected government of Yemen has been displaced by an Iranian-backed insurgency by minority Houthi militias.'
'The coalition is in Yemen with the support of the UN Security Council to restore the legitimate government. The coalition is operating in accordance with international humanitarian law, taking all practical measures to minimize civilian casualties. Every civilian casualty is a tragedy.'
The Saudi coalition does deny targeting civilians and claim that the August 9 bombing was a 'legitimate military operations.'
'The US has worked with the Saudi-led coalition to help them improve procedures and oversight mechanisms to reduce civilian casualties,' said Pentagon spokeswoman, Lt. Cmdr. Rebecca Rebarich.
'While we do not independently verify claims of civilian casualties in which we are not directly involved, we call on all sides to reduce such casualties, including those caused via ballistic missile attacks on civilian population centers in Saudi Arabia.'
The UN plans to conduct a separate investigation for the strike.
When prompted, al-Maliki claimed that the bus strike was a 'legitimate target'.
'No, this is not children in the bus,' he said. 'We do have high standard measures for targeting.'
Abdullah Al-Mouallimi, Saudi ambassador to the UN, claimed that 'the targeted Houthi leaders were responsible for recruiting and training young children and sending them to battlefields.'
In response to the bombing, US Secretary of State Mike Pompeo spoke with Saudi Crown Prince Mohammed bin Salman on Monday. The US is working to place distance between it and civilian bombings by placing pressure on the coalition.
'We are not engaged in the civil war. We will help to prevent, you know, the killing of innocent people. I'm very concerned about the humanitarian situation,' US Defense Secretary James Mattis. 'Wars are always tragic, but we've got to find a way to protect the innocent in the midst of this one.'