(NewsNation) —  Former President Donald Trump said the FBI agents “raided” his Mar-a-Lago estate in Palm Beach, Florida on Monday.

The focus of the investigation was not immediately clear.

While Trump is calling this a raid, former U.S. Secret Service special agent Evy Poumpouras told NewsNation the FBI executed a search warrant.

“It’s a search warrant at the end of the day. Now you want to call it a raid, some people can and it does give it a different sense or feel, and it’s actually what former President Trump used, but at the end of the day, it is a search warrant,” she said.

Poumpouras explained: “You have to have probable cause, you present it to a U.S. magistrate or judge, a neutral party. They give it to you, and then it clearly lays out what you’re looking for where you’re looking for it, what location within the house, where you can look for this stuff.”

Former U.S. attorney Henry Littman said the FBI would have needed to present a “bulletproof” case to a judge, given Trump’s status as a former president.

“I think we can be confident that in addition to the standard play, there were also very certain both that they would be able to show probably cause and they would give details of why they thought there’s evidence of a crime at Mar-a-Lago,” Littman said.

Poumpouras also detailed what the FBI needed to prove to obtain a search warrant to enter Mar-a-Lago.

“Investigators went to a neutral party, the U.S. magistrate, and said this is what we have. You cannot get a search warrant without probable cause. I will tell you this much to get a search warrant of this magnitude is not an easy thing,” she said.

“Also, they probably had a lot more than just probable cause to get it. This probably went through up the echelons, and people really thought thoughtfully about this before executing it because of the heat that it’s going to bring. It is unprecedented — this is something new. But again, it goes back into violation of the Presidential Records Act, which is that we cannot remove documents for the fear of having these documents destroyed — classified or top secret. So that’s what’s happening here.”

While this search, in essence, was for classified documents, Trump said that a personal safe was searched by agents. Poumpouras said everything agents are looking for is detailed in the search warrant and gives investigators an indication of where they can look. Warrants also curtail what law enforcement can and can’t do, so they don’t “just have carte balance and look wherever they want for whatever they want.”

“If I was looking for a larger object, let’s say a big screen TV, I can’t open drawers, I can’t look in small places,” Poumpouras said. “But if I’m looking for documents, thumb drives, I can look anywhere — that includes a safe.”