Connor Park, 22, a Sioux Falls Regional Airport security screener faces felony terroristic threat charges.
Officer Sam Clemens with the Sioux Falls Police Department said Park told a co-worker he was going to bring a gun and open fire on employees and his superiors.
"I think all the credit goes to this other employee that heard that information and passed it along,” said Clemens.
Authorities said the employee told the TSA-hired security contractor they worked for about the threat.
Clemens said the company then informed the TSA and went to police.
"We would rather know that information ahead of time and possibly prevent something as opposed to trying to pick up the pieces later,” said Clemens.
Police said they determined the threat to be credible after learning Park owned several firearms.
Clemens also said employees expressed their concerns to police during interviews.
"If they think it's credible, if they believe it can happen, then that's a big factor in it,” said Clemens.
Park was arrested at his home Thursday afternoon at the 6000 block of South Cliff Avenue in Sioux Falls.
Police said they did find weapons inside Park's house.
Any specific reason Park made the threats against his co-workers has not been determined by law enforcement.
The terroristic threat charges Park faces are currently at the state level and police said federal charges could be coming following a review by the U.S. Attorney's office.