Federal prosecutors charge Ryan Routh with attempted assassination of Donald Trump

Federal prosecutors have officially charged Ryan Routh with attempting to assassinate former President Donald Trump.

The indictment adds three counts, including attempted murder of a major presidential candidate, possession of a firearm in furtherance of a crime of violence and assault on a federal officer, to the two federal firearms charges Routh already faced.

The move was expected and anticipated both by prosecutors at a court hearing on Monday and by Attorney General Merrick Garland at a news conference on Tuesday afternoon.

“Violence against public officials endangers everything our country stands for, and the Department of Justice will use every tool available to hold Ryan Routh accountable for the attempted assassination of former President Trump charged in the indictment,” Garland said in a statement. “The Department of Justice will not tolerate violence that strikes at the heart of our democracy, and we will find and hold accountable those who perpetrate it. This must stop.”

He is expected to be arraigned on the charges at a court hearing next week.

Judge Aileen Cannon, the Trump-appointed judge who dismissed Trump’s classified documents case, has been randomly assigned to oversee the Ryan Routh case.

Routh, 58, had previously been charged with possession of a firearm as a convicted felon and possession of a firearm with an obliterated serial number for the incident that took place at Trump International Golf Club on Sept. 15.

Prosecutors on Monday released new details about their investigation, saying there is “probable cause to support additional charges that can and should be considered by the court.”

Routh had a list that included dates from August to October of places where Trump had appeared or was expected to be, and is suspected of having traveled near Trump’s golf course and Mar-a-Lago resort several times in the month before his arrest, prosecutors said in an arrest filing.

In their memo, prosecutors further revealed that Routh allegedly sent a letter “several months before” his arrest to a civilian witness that said, “This was an assassination attempt on Donald Trump, but I failed him.”

The government argued that the only reason Routh was in West Palm Beach on Sept. 15 and the month before was “for one reason and one reason only, and that was to kill the former President of the United States.”

On the day of the assassination attempt, Trump was playing golf on the course when a Secret Service agent spotted a gun barrel protruding from the tree line near the sixth green, according to investigators.

The officer then fired in the direction of the rifle and saw Routh fleeing the area and getting into his vehicle nearby, according to the criminal complaint filed in the case.

In the treeline area where the suspect was seen, officers found a digital camera, two bags, including a backpack, and a loaded SKS-style 7.62×39 caliber rifle with a scope, according to the complaint.

Trump was uninjured in the incident and was taken to safety by Secret Service agents.

ABC News’ Katherine Faulders and Aaron Katersky contributed to this report.