Law enforcement to hold briefing after apparent Trump assassination attempt | LIVE

The suspect in the apparent assassination attempt on former President Donald Trump may have been lurking near the Republican presidential nominee’s West Palm Beach golf course for nearly 12 hours before a Secret Service agent spotted him, according to a criminal complaint.

Multiple law enforcement sources told ABC News that the 58-year-old suspect, Ryan Wesley Routh, was detained by Florida authorities in relation to the incident. Authorities are now probing for more details on the would-be shooter.

According to the criminal complaint filed in the case, Routh’s cellphone dated tracked him near the tree line of Trump International Golf Club as early as 1:59 a.m. on Sunday.

As Trump was playing a round of golf that afternoon, a Secret Service special agent walking the perimeter of the golf course spotted what appeared to be a rifle poking out of the tree line. The agent then fired in the direction of the rifle and saw Routh fleeing the area and entering his Nissan vehicle, according to the complaint.

In the area of the tree line where the suspect was seen, agents 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. The serial number on the rifle “was obliterated and unreadable to the naked eye,” the complaint states.

Agents also found a black bag containing food, according to the complaint.

RELATED: What we know about Ryan Wesley Routh, the suspect in Trump ‘attempted assassination’

The latest details of the incident emerged as Routh appeared in West Palm Beach federal court on Monday morning. Prosecutors said he is charged with possession of a firearm as a convicted felon and possession of a firearm with an obliterated serial number.

Routh did not enter a plea to the charges, and was ordered to return to court on Sept. 23 for a pre-detention hearing. His arraignment has been scheduled for Sept. 30. Routh entered the courtroom wearing a T-shirt. He was seen smiling and nodding as he spoke to federal public defender Kristy R. Militello, who has been assigned to represent him.

When a judge asked Routh a series of questions to determine if he qualified for a public defender, Roth said he earns a monthly income of around $3,000, owns two trucks in Hawaii that are worth approximately $1,000 each, owns no real estate and has “zero” savings. He also informed the court that he has a 25-year-old son.

Trump thanks Secret Service

“I would like to thank everyone for your concern and well wishes – It was certainly an interesting day!” Trump said in a post on Truth Social.

“Most importantly, I want to thank the U.S. Secret Service, Sheriff Ric Bradshaw and his Office of brave and dedicated Patriots, and, all of Law Enforcement, for the incredible job done today at Trump International in keeping me, as the 45th President of the United States, and the Republican Nominee in the upcoming Presidential Election, SAFE.”

“THE JOB DONE WAS ABSOLUTELY OUTSTANDING. I AM VERY PROUD TO BE AN AMERICAN!” he wrote.

The former president is expected to meet Monday with the acting director of the Secret Service, Ronald Rowe Jr., sources familiar with the matter told ABC News.

Following the July 13 assassination attempt on Trump at a campaign rally in Butler, Pennsylvania, Trump, who was shot in the ear, also met with the former director, Kimberly Cheatle, at the time for a briefing.

RELATED: How the 1st assassination attempt on Donald Trump unfolded

Trump playing golf when gunman spotted

On Sunday afternoon, Secret Service agents accompanying Trump fired at a man armed with an AK-47-style rifle on or near the Trump International golf course on Sunday.

The FBI is investigating Sunday’s incident as an “attempted assassination.” Palm Beach County Sheriff Ric Bradshaw said at a news conference Sunday afternoon that the gunman was within 300 to 500 yards of Trump when he was spotted.

Secret Service agents fired four to six rounds at him before he dropped his weapon and fled the scene in a vehicle. Witnesses reported the license plate number to authorities, and the suspect was stopped and detained.

It was not clear if the suspect was aiming his gun at the former president. Agents fired at the suspect after spotting his rifle through the fence line, multiple sources told ABC News.

Sources said three shell casings believed to be associated with the suspect’s AK-47 were found on the scene, though investigators are still evaluating whether the suspect fired his weapon. The rifle and two backpacks containing a GoPro camera and ceramic tiles were recovered from the scene, Bradshaw said.

Authorities are now probing Routh’s background. The detainee is believed to have ties to North Carolina and Hawaii, sources said. Sources told ABC News that the FBI is conducting an extensive investigation into Routh’s social media activity, travel and any criminal record. Friends, family and associates are also being sought for interviews.

Suspect’s family grilled

The suspect’s family is telling investigators that while Routh had no diagnosed mental illness, he “fixated” on things, multiple sources briefed on the investigation told ABC News.

An avenue of investigation is whether Routh became fixated on Trump over the former president’s stance on Ukraine. Routh appears to have made recent social media posts critical of Trump and used social media to document his travel to Ukraine.

According to the sources, Trump was getting ready to putt on the fifth hole when a Secret Service agent called out “gun!” Agents immediately surrounded Trump and took him to a predetermined secure location at the property. USSS often has these safe areas designated in advance.

Sources familiar with the investigation said authorities are looking into whether Routh had grievances related to Trump’s position on Ukraine.

Authorities are expected to file more charges relating to the incident in the coming days, sources told ABC News.

Suspect’s criminal history

Routh has an extensive rap sheet in North Carolina dating back to 1997, including an incident from 2002 during which he reportedly barricaded himself inside a business while armed with an assault weapon, according to police and court records.

According to the Greensboro News & Record, in December 2002, Routh fled a traffic stop and barricaded himself inside a local roofing business for three hours until police arrested him.

Routh pleaded guilty to a felony count of possessing a weapon of mass destruction and a misdemeanor count of carrying a concealed weapon, court records show. State incarceration records show he was sentenced to probation for this incident. Court records also indicate he still owes a $225 assessment related to the felony charge of possession of a weapon of mass destruction.

Routh also pleaded guilty in 2003 to stealing a state-issued identification card and, in 2010, pleaded guilty to a misdemeanor theft charge. He was also repeatedly sued by construction contractors for attempting to write checks with insufficient funds.

Routh has several traffic citations, including speeding, running red lights, failing to wear a seat belt, driving while his license was revoked and driving with a broken windshield, among others.

Biden and Harris condemn apparent assassination

President Joe Biden and Vice President Kamala Harris both condemned the apparent assassination effort.

“In America, we resolve our differences peacefully at the ballot box, not at the end of a gun,” ” Biden said Monday while speaking in Philadelphia, Pennsylvania “America suffered too many times, the tragedy of an assassin’s bullet. It solves nothing. It just tears the country apart. We must do everything we can to prevent it and never give it any oxygen.”

Harris said she was “thankful” that Trump was safe and “deeply disturbed by the possible assassination attempt.”

“As we gather the facts, I will be clear: I condemn political violence. We all must do our part to ensure that this incident does not lead to more violence,” Harris said.

On Monday morning, Biden said he believes the Secret Service needs more help and called on Congress to act following the second apparent attempted assassination attempt on Donald Trump in nine weeks.

“Thank God the president is OK,” Biden said before boarding Marine One to depart the White House. “One thing I want to make clear: The service needs more help. And I think the Congress should respond to their needs if they, in fact, need more servicemen, and so that’s what we’re going to be talking about.”

Asked what kind of help he thought the Secret Service needs, Biden said, “They’re deciding whether they need more personnel or not.”

ABC News’ Lalee Ibassa, Katherine Faulders, Aaron Katersky, Soo Rin Kim, Michelle Stoddart, Pierre Thomas, Rachel Scott, Jack Date, Leah Sarnoff, Kelsey Walsh and Luke Barr contributed to this report.

CNN and the Associated Press contributed to this report.