College football player arrested in the shooting death of his transgender girlfriend

The 911 call to Tyler, Texas, police early in the morning of Jan. 26 first reported a car crash – and then, a witness nearby told police he'd heard gunshots.

Officers responding to the scene at 2:26 a.m. discovered a red Toyota Camry that had jumped the curb just shy of hitting a utility pole. The lone person inside, in the driver's seat, appeared to be female. The victim had been shot "several times," according to a criminal affidavit – and it was the shots, Officer Don Martin tells PEOPLE, that caused the victim to lose control of the car.

Declared dead at the scene was Tyrone "Ty" Lee Underwood, 24, a transgender woman.

On Feb 9, police arrested Carlton Ray Champion Jr., 21, a college football player who they say had an ongoing relationship with Underwood, for Underwood's murder.

In their investigation police interviewed Champion's father, Carlton Champion Sr., who "stated that he heard Carlton Jr. was meeting the victim and thought the victim was a female," Officer Nathan Elliott wrote in the arrest affidavit. "According to Champion Sr., Carlton Jr. was supposed to get some type of sexual favor from the victim but realized the victim was a male."

Police say otherwise. A relationship between the two had been ongoing for several weeks, Martin tells PEOPLE. "All indications are that both parties, the suspect as well as the victim, knew the gender of each prior to the shooting."

"There's no hate crime," Martin says. "Evidence that was located indicate that they were both aware – through more than a friendship relationship – what they were getting into." It was, he says, "a sexual relationship."

Underwood died, according to the arrest affidavit, after arguing with Champion over social media about whether Champion was seeing someone else.

How and where the gunshots were fired is under investigation, police say.

Although police have located no witnesses who saw anyone running from the car, "the indications by the bullet holes in the vehicle and the victim indicate that more than likely, at some point in time, Champion was in the vehicle, versus not a drive-by" shooting, says Officer Martin. "We definitely know for sure" that shots were fired from outside the vehicle, he says, "but possibly inside as well."

Investigators were led to Champion after Underwood's roommate told them Underwood had been dating a man named "Carlton" for the past couple of weeks. A police department employee who worked with Underwood recalled that Underwood had talked about dating a football player at Texas College in Tyler.

Police located Carlton Champion on the team's roster. Champion said he'd been communicating with Underwood through the Kik social media app. Messages on Underwood's cell phone showed contact with Champion as far back as Jan. 19 and documented the pair's "sexual relations," according to the affidavit.

Starting the night of Jan. 25 and into the early morning of Jan. 26, Champion texted Underwood to ask if Underwood wanted to "chill." They planned to meet and texted over several hours before Champion fell asleep and Underwood became mad, the affidavit states.

When Underwood sent Champion a message that she didn't want to see Champion anymore, Champion responded, "That's how it is now" and "I will make it up."

Champion told Underwood to come get him. Underwood replied by text, "Carlton bro you saw me kiking you at 11:00 but you chose to be with whoever you was with and no you think you can just (expletive) with me when you want." Ongoing exchanges as late at 2:06 a.m. documented further plans and locations to meet – all inconsistent with Champion's initial statement to police that communication between the two had ended about 11 p.m.

Asked to explain his inconsistencies, Champion "became defensive and uncooperative," the arrest affidavit states. Confronted with surveillance video that showed him leaving his campus dorm at 2:13 a.m. and returning around 2:27 a.m., "Champion would only say that he didn't leave the dorms."

Tests on the camouflage jacket Champion was seen wearing as he left Texas College's Daniel Hall registered a "positive reaction" for blood, according to the affidavit.

Champion is being held in Gregg County jail on a $1 million bond. At press time, he has not yet entered a plea. PEOPLE