Charlie Kirk's alleged assassin lived with transgender partner who is now cooperating with FBI: Officials

EXCLUSIVE: Charlie Kirk’s alleged assassin lived with his transgender partner, senior-level FBI officials told Fox News Digital.

Bureau officials confirmed that Tyler Robinson, 22, was in a "romantic relationship" with the unnamed person, who is a male transitioning to a female, and that they shared an apartment in Saint George, Utah. Those FBI officials told Fox News Digital that Robinson's partner is fully cooperating with the FBI's investigation.

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One FBI official told Fox News Digital the individual has been "extremely cooperative," and said the person "had no idea" Robinson was allegedly planning to assassinate the Turning Point USA founder. The person is not currently accused of any criminal activity in connection with the assassination.

FBI officials told Fox News Digital that the FBI had text messages and other communications between Robinson and his partner that helped FBI agents zero in on Robinson. Officials said the FBI took evidence from their apartment, including computers, which has been sent to Quantico for review, Fox News Digital has learned.

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The FBI declined to comment on whether Robinson's partner would be charged with a crime.

"The FBI is investigating a record number of tips," an FBI spokesperson said. "Every connection, every group, every link will be investigated and anyone involved in this matter, anywhere in the world they might be, will be brought to justice."

The apartment Robinson and his partner shared is in the same southern Utah community Robinson's parents live in. It is approximately four hours away from Utah Valley University, where Robinson allegedly shot Kirk.

Kirk was killed Wednesday as he spoke to a crowd at the school's campus in Orem. Authorities believe a single shot was fired from the roof of a building some 200 yards away. Kirk was 31, and the married father of two young children.

Moments before Robinson allegedly shot Kirk, an audience member asked Kirk: "Do you know how many transgender Americans have been mass shooters over the last 10 years?"

Kirk replied: "Too many."

Kirk was then asked: "Do you know how many mass shooters there have been in America over the last 10 years?"

Kirk replied: "Counting or not counting gang violence?"

Kirk was then assassinated.

A law enforcement source told Fox News Digital that Robinson’s father, who ultimately turned him in to authorities, told the FBI that he recognized his son from surveillance video images which FBI Director Kash Patel directed to be made public as the 33-hour manhunt unfolded.

The source told Fox News Digital that when Robinson arrived at his father's home, he said he wanted to kill himself. The source told Fox News Digital that the father spoke with a minister the family knew before turning in his son.

Meanwhile, the rifle that the FBI believes was used to kill Kirk contained ammunition inscribed with anti-fascist messaging.

Utah Gov. Spencer Cox confirmed the messaging at a news conference Friday, saying investigators discovered inscriptions on casings found with a bolt-action rifle near the campus.

One used casing and three unused casings contained the writings, Cox said.

News of the ammunition inscriptions was first shared on social media Thursday morning in a preliminary bulletin attributed to the Bureau of Alcohol, Tobacco, Firearms and Explosives.

This is a developing story. Please check back for updates.