Dallas (CBS11) – The Dallas detective who was the first to interrogate Lee Harvey Oswald does not expect much new information to come from the Thursday release of sealed documents pertaining to the assassination of President John F. Kennedy.

James “Jim” Leavelle has answered questioned surrounding the assassination for five decades.

READ MORE: Jail Escapee Arrested Trying To Flee Texas At Southern Border

“They’re thinking they’re going to find something new that nobody ever knows about,” said Leavelle.

Known for his tan suit and tall cowboy hat, Leavelle was the man to Oswald’s right as Jack Ruby shot and killed Oswald.

Leavelle was helping transfer Oswald when the shot was fired.

“You got a job to do and I had a job to save that man’s life,” said Leavelle. “That’s what was all going through my mind.”

While the image of Leavelle and Oswald is famous, many might not realize all the work investigators like Leavelle poured into the case.

“We checked it out to my satisfaction and to everybody else,” said Leavelle.

READ MORE: Supreme Court To Consider Challenge To Harvard And UNC Affirmative Action Policies

Their hard work has never satisfied some who feel investigators have held back information.

There are details they are hoping will surface Thursday when President Trump signs off on the release of the final batch of classified JFK documents.

“To tell you the truth, I don’t give it much thought at all because I know pretty much what’s in all of them,” said Leavelle.

He will not talk about everything that is currently classified, Leavelle still does not think the release will reveal much about Oswald’s unexplained trip to Mexico City weeks before the assassination or any other secrets.

“A lot of people are going to be disappointed I think,” said Leavelle. “They think they’re going to find a new suspect and all of this and those things and they’re not going to find it…because it’s not there.”

To those who still will not be satisfied, Leavelle has a message.

MORE NEWS: Hill County Home To $2M Texas Lottery Winner

“Well I’ll just tell you’ll have to keep looking and see if you find anything,” said Leavelle. “I can’t help you. I can’t build something that’s not there.”