The suspect arrested in the fatal shooting of Charlie Kirk had an “obsession” with the conservative influencer, based on the alleged shooter’s digital footprint, FBI Co-Deputy Director Dan Bongino said Monday on Fox News.

Tyler Robinson, a 22-year-old Utah native, is accused of fatally shooting Kirk during an event at Utah Valley University on Sept. 10.

Bongino said the suspect appeared to have exhibited “multiple warning signs.”

“I believe co-workers stated he had detached himself when the topic of politics came up and walked away,” Bongino said on Fox News’ “America’s Newsroom.”

Bongino said they are looking into whether anyone knew the shooting could happen and didn’t alert authorities, referring to online chats Robinson allegedly had about Kirk.

“Did they … hear it and think it was a joke? That is what we’re trying to find out now,” he told Fox News. “If there is a larger network here, we will get that out to the public as soon as we can.”

FBI Director Kash Patel also announced on “Fox & Friends” that DNA found at the crime scene, specifically the towel wrapped around the firearm used in the shooting, and on a screwdriver, links Robinson to the killing of the conservative influencer.

Law enforcement officials have also discovered evidence that Robinson was tracking Kirk’s events and public appearances through public information on the internet, law enforcement sources familiar with the investigation told ABC News.

Officials also told ABC News they have gathered evidence showing Robinson had gained a familiarity with the Utah Valley University campus, including looking at maps of the campus in the days before the attack.

Robinson was arrested last week for felony discharge of a firearm, aggravated murder and obstruction of justice, according to probable cause documents, and was booked into the Utah County Jail. He could also face federal charges, sources said, though it’s unclear what those would be.

Utah’s Department of Public Safety and a source in the state’s attorney’s office said they expect charges against Robinson will be filed by Tuesday.

Investigators continue to assess evidence, including looking at electronic devices the suspect may have had access to, as federal charges could be announced in the coming days, law enforcement officials told ABC News.

A motive has not been revealed by officials, despite Vice President JD Vance saying “left-wing extremism” is “part of the reason” Kirk was killed.

Robinson was apprehended after his father recognized him in photographs released by authorities, Cox said on Friday. His father told Robinson to turn himself in, with the 22-year-old initially saying no, but later changing his mind, officials said.

Just before 10 p.m. on Thursday, Robinson, his father and a close friend who previously worked in law enforcement — who is also a youth volunteer with a local Church of Jesus Christ of Latter-day Saints — drove together from Washington, Utah, to the Washington County Sheriff’s Office in Hurricane, according to Sgt. Lance Alfred, a spokesperson for the sheriff’s office.

During the drive, the family friend called the personal cellphone of the Washington County Sheriff’s Office patrol division chief to report the suspect was about to turn himself in, Alfred told ABC News.

When Robinson arrived at the sheriff’s office, he was taken into a building marked “Authorized Personnel Only,” with personnel from the sheriff’s office notifying the Salt Lake City FBI office and other local law enforcement officials of the suspect’s arrival, Alfred said.

Robinson was kept in the back offices of the sheriff’s office and turned over to the FBI and other law enforcement upon their arrival, which was just before 6 a.m. on Friday.

Cox thanked Robinson’s family last week, saying, they “did the right thing.”

Investigators also interviewed a family member of Robinson who said the suspect had “become more political in recent years,” Cox said.

In a recent incident the family member detailed to investigators, Robinson came to dinner and in a conversation with another family member he mentioned Kirk was coming to Utah Valley University. They talked about why they didn’t like him and his viewpoints.

President Donald Trump, who announced Friday on “Fox & Friends” that the suspected shooter was in custody, said Robinson should get the death penalty.

“In Utah, you have death penalty, and a good governor there, I have gotten to know him,” Trump said of Cox. “The governor is intent on the death penalty in this case and he should be.”

In a press briefing from the Oval Office Monday evening, Trump said it appeared Robinson became radicalized on the internet.

“Something happened to him over a fairly short period of time. It looks like he was radicalized over the internet, and it’s radicalized on the left. He’s a left,” Trump claimed.

Before the arrest of the alleged shooter, officials said they had obtained “good” video footage of the individual and were able to track the movements of the suspect.

On the day of the shooting at approximately 11:52 a.m., the suspect arrived on the Orem campus and then proceeded to travel through the stairwells up to the roof of the building near where the outdoor event was taking place, before the suspect fired down at Kirk, Utah Department of Public Safety Commissioner Beau Mason said last week.

Kirk was hit by a single shot at approximately 12:20 p.m. and taken to a hospital, where he was pronounced dead, authorities said.

After the shooting, the suspect traveled to the other side of the building, jumped off and fled off-campus into a neighborhood, Mason said.

On Friday, Erika Kirk, the conservative commentator’s wife, said “no one will ever forget my husband’s name.”

“You have no idea the fire that you have ignited within this wife, the cries of this widow will echo around the world like a battle cry,” Erika Kirk said on Friday in her first public message since her husband’s death.

ABC News’ Pierre Thomas, Luke Barr and Mike Levine contributed to this report.