Federal agents arrested a 17-year-old from McKinney, Texas, on Oct. 5 in what investigators believe was a plot to assassinate Rep. Keith Self at a local event and to carry out a separate terrorist attack in North Texas on behalf of ISIS, according to federal law enforcement sources cited by the local news outlet WFAA.

The teenager was taken into custody after he acquired a firearm, Fox News reported, drawing on the same sources. According to those accounts, he intended to target the congressman at an event in the McKinney area on Saturday, Oct. 17, nearly two weeks after his arrest. He remains in federal custody, and his name has not been released because he is a juvenile.

Self, a Republican who represents Texas' 3rd Congressional District, confirmed the threat on Wednesday. "I am grateful to the FBI and law enforcement for stopping this threat," he said in a statement posted on X. "My family and I are safe, and I remain focused on serving the people of Texas' 3rd District."

The congressman told CBS News Texas that he was never in any real danger. By the time the U.S. Capitol Police notified him of the threat, he said, federal authorities already had the teenager in custody. "When we knew about it, they had him," Self said. Law enforcement told him the boy had planned to make waves, "perhaps try to shoot at me," and carry out a terrorist attack, but Self said he did not know the wording of the threat or how or where it was made. "The FBI, through the Capitol Police, only tells us so much," he said.

He said he understood that authorities had "known about this kid for a while," and KRLD reported that agents had been monitoring the teenager after he was recently radicalized. Self gave the bureau credit for moving before anything happened. "So often we hear that somebody does something and then you find out later that the FBI had him on some sort of watch list and didn't take action," he told the station. "So I am very grateful that the FBI took action in this case."

Threats against lawmakers are "more routine than you would think," Self said. He has received them before, "but not to this degree and not any that action was taken by law enforcement." A veteran of 25 years in the military who deployed multiple times, he said he was not fazed, in part because he knew law enforcement had the teenager under control. "Now, it would have been a little different if they had said, 'There's an unknown threat out there,'" he said.

Self declined to speculate to CBS about what motivated the alleged plot, though he said the teenager was "somehow under the influence of the things that we see happening in Texas and certainly in McKinney." When WFAA asked whether his public stance against Islamic extremism made him a target, he said he could not be certain. "If it's ISIS related, you kind of have to believe that. I can't prove that. I don't know that for sure," he said, according to Fox News.

Self has been an outspoken critic of Sharia law and of what he calls radical Islam. He co-founded the Sharia-Free America Caucus with Rep. Chip Roy of Texas, and last month he introduced a nonbinding resolution denouncing Sharia law and opposing its implementation in the United States. In his written statement, he said that "preserving our constitutional republic from radical Islam means accepting the costs that come with it," costs he listed as "name-calling, threats, and worse." "This only strengthens my resolve," he wrote. "I will not back down."

Much about the case has not been made public. According to KRLD, authorities have not described the charges or said whether prosecutors will seek to try the teenager as an adult. No injuries were reported. CBS News Texas said its efforts to reach the FBI and the Capitol Police for comment were unsuccessful, and as of Thursday morning there appeared to be no official report on the case, Just the News noted. The investigation is continuing.