FBI agents descended on the Montevideo mobile home belonging to the parents of Buford “Bucky’’ Rogers in May because a witness in Texas had told them Rogers was on the verge of carrying out multiple bombings, an FBI agent testified Tuesday.

Appearing in a St. Paul federal courtroom, FBI agent Shane Ball said the same witness had told federal agents that Rogers had cheered the Boston Marathon bombing and was about to carry out plans of his own to bomb the Montevideo Police Department, a communications tower and a National Guard armory.

“It was a very real plot,” Ball said.

He did not name the witness, who Ball said was the sole source of information on the alleged plot that led to the May 3 raid.

Although the FBI labeled it a terror case in a news release issued after the arrest, a federal grand jury did not indict Rogers on terrorism charges when it released its report three weeks later. He was indicted on four felony counts, including being a felon in possession of a firearm and three counts of possessing “unregistered destructive devices.” The devices included two Molotov cocktails, two “black powder nail devices” and a pipe bomb.

Rogers, 24, was seated in the courtroom dressed in orange prison garb Tuesday. His father and mother, Jeff and Margaret Rogers, and Rogers’ brother and fiancée sat in the back of court.

“The people they have as witnesses are lying through their teeth,” Jeff Rogers said afterward. He said the FBI’s witness, whom he did not name, previously lived in the mobile home with the family.

Miranda warning delayed?

Andrew Mohring, Rogers’ federal public defender, is seeking to suppress much of the evidence, including an interview Rogers gave to the FBI immediately after his arrest.

For the first 40 minutes of that interview the FBI didn’t give Rogers the Miranda warning that he was entitled to an attorney and that his statements could be used against him. Ball said the warning was not needed because of an immediate public safety concern.

Later in the interview, Rogers was read his Miranda rights and Ball continued to question him.

Responding to questions Tuesday by prosecutor Andrew Winter, Ball said the FBI witness left Minnesota because his girlfriend heard of the plot and wanted no part of it. He went to Texas, then told the San Antonio police about it.

The FBI was called, and agents spoke to him May 2. He told them the attacks would occur by midnight May 4, Ball said.

The witness also told the FBI that Rogers “cheered” the April 15 Boston Marathon bombing.

Rogers was a member of the Black Snake Militia, the witness told the FBI. “He thought it was a militia hate group,” said Ball, adding that the group was limited to four members of the Rogers family.

The witness told the FBI bomb devices and guns were in the mobile home and that Jeff Rogers once had opened fire through a window when he thought law enforcement agents were approaching.

After listening to the witness, the FBI assembled about 50 officers that included an FBI SWAT team and county and Montevideo police. They drove to the mobile home in two armored carriers and ordered people out of the home through a loudspeaker, Ball said. There was no violence, and Buford Rogers was later arrested at his residence elsewhere in Montevideo. He was taken to the police station and interviewed by Ball and Adam Christopher, the Montevideo police chief.

Documents unsealed

U.S. Magistrate Judge Jeanne Graham, who presided at Tuesday’s hearing, also ordered the unsealing of six documents in the case at the request of the Star Tribune attorney John Borger. Graham sealed the documents July 11 following a motion by Mohring. But after arguments by Borger and a separate session closed to the public and media, she said she found the arguments to seal the documents “not sufficient.”

Those documents include the search warrant that led to the raid and related paperwork. They were not yet available late Tuesday.