Donald Trump’s attempt to blame Iran for the deadly strike on an elementary school stemmed from an early US intelligence assessment that initially suggested the missile was Iranian but was almost immediately dismissed, according to two people familiar with the matter.

The CIA initially told the president that they did not believe the missile that struck the school was a munition used by the US because the fins appeared to be positioned too low for it to be a Tomahawk cruise missile.

Within 24 hours, the CIA realized that early assessment had been wrong after it became clear from additional videos, taken at other angles, that the missile was in fact a Tomahawk, the people said on the condition of anonymity to discuss sensitive deliberations.

But Trump had already settled on the explanation that Iran was responsible for the strike before he raised it to reporters on Air Force One last Saturday, even as the defense secretary Pete Hegseth was more cautious and said only the matter was under investigation.

Trump repeated his position at a news conference the following day. While he appeared to accept the missile that hit the school was a Tomahawk – a missile used only by the US and a handful of allies including the UK, Japan and Australia – he suggested it belonged to Iran.

It was not clear when Trump was briefed about the updated intelligence findings but former intelligence officials faulted both Trump and the briefers.

“Giving Trump preliminary information is dangerous because he can turn it into a total embarrassment,” one former CIA officer said, speaking on the condition of anonymity. “If the principal asks you a question, the best thing to say is you don’t know, knowing how hard it is to go back later to correct the record.”

The president’s efforts to pin responsibility on Iran comes as an ongoing Pentagon investigation into the strike has reached similar conclusions, finding that the missile in question was a Tomahawk fired by the US military, which relied on outdated intelligence.

The strike is believed to have killed at least 175 people, many of them children, making it one of the deadliest targeting errors in recent decades. The Pentagon investigation has been focused on why the intelligence was outdated and whether it was double-checked.

In a statement, White House spokesperson Anna Kelly said: “This investigation is ongoing. As we have said, unlike the terrorist Iranian regime, the United States does not target civilians.” A CIA spokesperson did not respond to a request for comment.

The school, located in the town of Minab, was on the same block as an Islamic Revolutionary Guard Corps navy base. The school building was once part of the military compound, but it appeared to have been walled off and converted into a school some time between 2013 and 2016.

Targets for airstrikes are typically produced by the Defense Intelligence Agency and the National Geospatial-Intelligence Agency, which looks at satellite imagery to build “target databases” on a product called Maven Smart System, according to a former senior defense official.

Designating a building as a target is done by specialized analysts years in advance with layers of oversight, the official said, but once entered into the database as a possible target, it may not necessarily be reviewed again until a strike is considered.

Military planners can then generate “target lists” from the database in Maven, including through the use of artificial intelligence tools, such as Claude, Anthropic’s large language model.

Those lists can be adjusted to prioritize different metrics, such as distance to the target or the probability of destruction. For the opening phase of the Iran war, the the list of potential targets ran into the thousands. It remains unclear whether each was verified before the strikes were carried out.