19-Year-Old College Student Found Stabbed To Death In Burnt-Down Apartment

When Arlington Police Department Detective Tommy LeNoir entered the fire-ravaged apartment of 19-year-old Missy Grubaugh, he was met with an “absolutely horrific” crime scene.

“I’ve seen bad crime scenes, and I’ve seen crime scenes involving people that were burnt in fires. This was elevated … Even with the smoke damage and the burn damage, you could still see that this was a victim of a very brutal assault,” Det. LeNoir told Oxygen's “An Unexpected Killer." “This child went through hell.”

In the bedroom, investigators found Grubaugh’s body, lying face-up on the bed. She had trauma to her head, and there was a puncture wound in the middle of her chest. An autopsy report later determined she was dead before the fire started and that the stabbing had been fatal, going through her heart and damaging her left lung, which caused massive internal bleeding.

The University of Texas at Arlington student had also been sexually assaulted, according to Fort Worth medical examiner Marc Krouse.

“This was a rape-homicide by a very aggressive perpetrator,” Krouse told “An Unexpected Killer.”

Although most of the physical evidence was destroyed in the fire, semen was recovered from Grubaugh’s body and submitted for DNA analysis.

By speaking with Grubaugh’s mother, Patty McIlhaney Grubaugh, detectives learned that in the days leading up to her murder, Grubaugh had spent an evening talking with her co-worker and neighbor, Luis Arroyo, for whom she sometimes babysat. The two had also engaged in a pillow fight, which was odd to investigators.

“This is strange,” Det. LeNoir said. “A 32-year-old man had a pillow fight with her. It caught my attention immediately.”

Management described the father of two and Army veteran as a model employee, but one co-worker told detectives something that led to Arroyo becoming the prime suspect: After Grubaugh’s murder, Arroyo told his co-worker, “I hope they catch that son of bitch that killed and raped Missy.”

Grubaugh’s sexual assault, however, was a detail that was never released to the public. Det. LeNoir set up an interview with Arroyo, who was forthcoming about his friendship with Grubaugh until they asked him to provide a DNA sample to test against the evidence found at the crime scene.

“His response immediately was, ‘What are you talking about? Wasn’t the evidence all burnt up?’ … You can see the concern in his face,” Det. LeNoir told “An Unexpected Killer.”

Arroyo then abruptly left the interview, promising to come back in a few days so investigators could collect his DNA sample. But, Arroyo never showed.

When detectives reached out to his work, they learned that his wife, Jeanette Arroyo, had called and told management that he needed to leave town.

Jeanette was brought in for questioning, and she told investigators that on the night of the murder, Luis left their apartment around midnight, returning two hours later. He took a shower and left the apartment for a second time, and when he came back, he was coughing and smelled of smoke.

He told Jeanette he was out for a jog and saw that Grubaugh’s apartment was on fire. Luis said he went inside and found her body on the bed and tried to perform mouth-to-mouth resuscitation. He claimed he was then overcome by the smoke and had to leave the apartment.

Neither Jeanette nor Luis called 911, and the couple went to sleep without reporting the fire.

“The story’s so bizarre, but she didn’t question him,” Det. LeNoir said. “And I don’t think she ever really saw it for what it was until she actually sat down and started telling me. And as she’s telling me, reality is setting in as far as what Luis might have done.”

Detectives obtained a search warrant for the couple’s apartment, where they found Luis’ military dog tags listing his blood type, which ended up being a match to Grubaugh’s attacker. With this evidence, investigators were able to issue an arrest warrant.

Luis was still in hiding, however, and it wasn’t until detectives revealed to Jeanette that Grubaugh had been sexually assaulted that she gave up her husband’s location. He was arrested without incident in San Antonio and charged with Grubaugh’s murder.

In the interrogation room, Luis claimed he had consensual sex with Grubaugh and admitted that he had stabbed her, but he denied setting the fire. Investigators collected his DNA, and it was found to be a match to the DNA from the sexual assault kit.

Luis was found guilty of capital murder and sentenced to life in prison, according to court documents.

To learn more about Luis’ motive and find out how investigators tracked him down, watch “An Unexpected Killer” on Oxygen.