WASHINGTON - Utah prosecutors filed a murder charge on Tuesday against the man accused of assassinating US conservative activist Charlie Kirk while releasing new details of the high-profile case.

Tyler Robinson, the leading suspect in the sniper death of Kirk, faces multiple charges, including aggravated murder, obstruction of justice, felony discharge of a firearm causing serious bodily injury, witness tampering, and commission of a violent offense in the presence of a child, Utah County Attorney Jeff Gray told a press conference.

Robinson made an initial court appearance on Tuesday afternoon via video from jail. During the virtual hearing, Gray presented all seven charges against Robinson and scheduled his next hearing for Sept 29.

READ MORE: Accused sniper jailed in Charlie Kirk killing awaits formal charges in Utah

The court also revealed private text messages in which Robinson was alleged to have privately confessed to the fatal shooting.

According to transcripts of messages in court documents, Robinson told his roommate when asked why he had committed the murder: "I had enough of his hatred. Some hate can't be negotiated out."

Robinson also left a note for his roommate hidden under a keyboard that said, "I had the opportunity to take out Charlie Kirk and I'm going to take it," according to Gray.

At a press conference, Gray said he had decided to seek the death penalty "independently, based solely on the available evidence and circumstances and nature of the crime."

Earlier on Monday, Federal Bureau of Investigation (FBI) Director Kash Patel said investigators have found DNA evidence tying alleged Kirk assassin Robinson to last week's crime scene.

Kirk, a right-wing activist and influencer, was fatally shot in the neck on Sept 10 while debating in front of the audience during an event at Utah Valley University.

"We have the DNA on the screwdriver that was found on the rooftop and the towel that the firearm was wrapped in," Patel said in an interview with Fox News.

The FBI director also said that the suspect's family has collectively told investigators that he subscribed to "left-wing" ideology and "even more so in these last couple of years."

The suspect had an "obsession" with Kirk, based on the suspected shooter's internet activity, FBI Co-Deputy Director Dan Bongino said Monday on Fox News.

Bongino said authorities are investigating whether anyone believes a shooting could have occurred but did not alert law enforcement, referring to chats online that the suspect allegedly had about Kirk.

Utah Governor Spencer Cox told local media on Sunday that Robinson was not cooperating with law enforcement and had not confessed to carrying out the shooting, but all people around are cooperating.

The governor told CNN on Sunday that the alleged shooter's friends and family had disclosed that Robinson was deeply indoctrinated with leftist ideology.

Cox also said that the suspect's roommate, also his romantic partner, was currently "transitioning from male to female", adding that he did not yet know whether that information was relevant.

"We're interviewing all kinds of people - everyone that knows him - and trying to learn more about what the motive actually was," Cox said.

Kirk's death has become a divisive issue over the past several days, underscoring political divisions in the nation.

READ MORE: Conservative influencer Charlie Kirk shot dead, manhunt on for suspect

Online, few people are having real discussions about gun violence; instead, the focus seems to be a blame game. Some accuse the "radical left" of suppressing free speech and even resorting to violence against those who invite peaceful debate, while others fault conservatives for fueling hatred and for their hypocritical silence when Democratic leaders were attacked.

"We have deeply polarized politics, with many Americans viewing the other party not as wrong but as an existential threat," Christopher Galdieri, a political science professor at Saint Anselm College in the northeastern state of New Hampshire, told Xinhua.

"While many leaders admirably condemned Kirk's killing and political violence generally, and urged people to stay calm and wait for the facts, we saw the Trump Administration spin up talk about going after people who 'contributed to' the shooting," Galdieri said.