Just two days after the nation memorialized the deaths of thousands of Americans who died in 9/11, President Donald Trump took to Twitter to deny the deaths of thousands of Americans who died due to Hurricane Maria, and the dismally slow government aid response.

In his tweets, Trump was referring to a report authored by a team of public health experts from George Washington University and commissioned by the government of Puerto Rico. The report, published in August, calculated the death toll in Puerto Rico due to the devastating impact and after effects of Hurricane Maria last fall.

Despite initial government estimates that as few as 64 people died due to the storm, the researchers found that nearly 3,000 people had died during and following the hurricane who wouldn’t have otherwise died. Many of these deaths were due to lack to access to healthcare, power, and clean water, the report found. The report calls this “excess mortality.”

“The results of our analysis of total excess mortality by socio-demographic subgroups show that every social stratum and age group was affected by excess mortality,” the report said.

Contrary to Trump’s suggestion, the stark change in death toll wasn’t politically-motivated arbitrary inflation—the researchers didn’t just total every death on Puerto Rico following the hurricane and claim it was due to the storm. Rather, they used an established method of public health research: they calculated what the average death rate was for Puerto Rico in the past, then projected that into the future to see what the death rate should have been if there had been no storm.

They also accounted for the mass exodus of Puerto Ricans who fled the island after the storm, and compared the numbers with the total change in population. Using this technique, they were able to show that even with the normal death rate and the mass migration, there were 2,975 more people who died after the storm than would have in a normal year. This is 22 percent higher than the number of deaths that would have been expected during that period in a year without the storm.

“Hurricane Maria led to a large number of excess deaths throughout the island,” Carlos Santos-Burgoa, the principal investigator of the project and a professor of global health, said in a press release at the time. “Certain groups—those in lower-income areas and the elderly—faced the highest risk.”

Hurricane Maria, a Category 5 hurricane, battered Puerto Rico and Dominica in September of last year. It killed thousands, caused billions of dollars in damage, and the island is still digging out from much of the destruction—power was only fully restored to the island three weeks ago.

Along with a more accurate estimate of the death toll, the GWU report also made recommendations for policies that could be put in place to prevent this kind of devastation in the future, such as creating a Crisis and Emergency Risk Communication Plan to better prepare the public for natural disasters. But it seems the president has decided to write it off instead.

As the East Coast prepares for another monstrous hurricane set to make landfall Friday, the president’s misconstruing of important lessons from another recent natural disaster is particularly unsettling.