In an appearance on Fox News, Patel also said investigators believe the suspect wrote a physical note saying he had the "opportunity to take out Charlie Kirk" and would do so. The note was destroyed, Patel said, but investigators have collected forensic evidence that it had existed and confirmed its contents through interviews.
Patel did not offer more details on who had received the text message or whether anyone had seen the written note before the attack. Investigators have not publicly identified a motive. Law enforcement authorities have said they believe the suspect acted alone when he shot Kirk but are investigating whether anyone else had a role in plotting the killing.
Separately, the Washington Post reported on Monday that Robinson had sent a message via the online platform Discord to friends apparently confessing to the crime.
"It was me at UVU yesterday. im sorry for all of this," read a message from the account belonging to Robinson that was sent on Thursday night, shortly before he was arrested, the newspaper reported, citing two people familiar with the chat as well as screenshots it had obtained.
Kirk, an influential ally of President Donald Trump who co-founded the leading conservative student group Turning Point USA, was killed by a single rifle shot last Wednesday during an event at Utah Valley University in Orem, about 65 km south of Salt Lake City.
Robinson is expected to be formally charged no later than Tuesday, when he is scheduled to make an initial court appearance. He remains in custody in a Utah jail.
Patel told Fox News that DNA matching that of the suspect, 22-year-old Tyler Robinson, was found on a towel that was wrapped around the rifle believed to be the murder weapon and on a screwdriver found on the rooftop from where authorities say the shooter fired.
Robinson has not cooperated with authorities, Utah Governor Spencer Cox said on Sunday, but investigators have been interviewing his friends and family in an effort to determine the motive for the shooting.
The killing has shaken a country that has experienced a spike in political violence, stoked by deepening polarisation between the right and the left.
Some Republicans, including Trump, have blamed liberal groups for Kirk's murder despite a lack of evidence, while Democrats have noted that left-wing figures have also been the targets of political violence in recent years.
In an appearance on Kirk's eponymous podcast on Monday, Vice President JD Vance said the "incredibly destructive movement of left-wing extremism" had helped lead to Kirk's killing.
While Robinson was raised by religious parents in a deeply conservative region of the state, "his ideology was very different than his family," Cox said on Sunday on NBC's Meet the Press program, without going into specifics.
State records show Robinson had registered as a voter without choosing a political party affiliation and had not voted in the 2024 presidential election. But a relative told police that Robinson had grown more political and had expressed dislike for Kirk in a recent conversation.
Kirk's killing was the latest in a series of high-profile episodes of US political violence. Last year, Trump was the subject of two assassination attempts, including one in which his ear was struck by a bullet.
In April, a man started a fire at the home of Democratic Pennsylvania Governor Josh Shapiro, though the governor and his family escaped harm. In June, a senior Democrat in Minnesota and her husband were assassinated in their home, and a man threw Molotov cocktails at a pro-Israel march in Colorado, killing one.
In August, a gunman obsessed with COVID-19 conspiracies fired at the Centers for Disease Control and Prevention headquarters in Atlanta, killing a police officer.
House Speaker Mike Johnson, a Republican, hosted a vigil for Kirk at the Kennedy Center in DC on Monday.
