Derrick Sean O'Brien

Late on the night of June 24, 1993, two teenagers—14‑year‑old Jennifer Ertman and 16‑year‑old Elizabeth Peña—cut across a set of railroad tracks on their way home. ^[1] They never made it.

On the same night, a small Houston gang calling itself the “Black and Whites” was out near those same tracks, celebrating the initiation of a new member. ^[1] Among the names that surface in the court record from that gathering is Derrick Sean O’Brien, listed alongside other young men who would soon be at the center of one of Houston’s most notorious crimes. ^[1]

By the time the girls’ bodies were found, they were so badly decomposed that dental records were needed for identification. ^[1] The medical examiner later concluded both died from trauma to the neck consistent with strangulation. ^[1]

The “Black and Whites” and a violent initiation

According to trial evidence, Peter Anthony Cantu was the self‑appointed leader of the Black and Whites, a gang operating in Houston. ^[1] On June 24, 1993, the group met to initiate a new member, Raul Villareal. ^[1]

The initiation was brutal but, at first, inward‑facing: Raul was required to fight each gang member for five to ten minutes. ^[1] After he’d gone through all of them, the group formally welcomed him into the gang. ^[1]

Present at this gathering, the record notes, were Roman Sandoval, Joe Medellin, Efrian (Efrain) Perez, and Derrick Sean O’Brien, along with Cantu himself. ^[1] Roman’s brother Frank and Joe’s fourteen‑year‑old brother Venancio were also there. ^[1]

After the fighting ended, the group shifted from ritual to aimless roaming. They drank beer, joked and roughhoused, then headed toward a set of nearby railroad tracks. ^[1] Those tracks are where their path collided with Jennifer Ertman and Elizabeth Peña’s. ^[1]

Two girls heading home

Around 11:30 p.m., Jennifer and Elizabeth decided to leave a friend’s house. The plan was simple: walk to Elizabeth’s, then have Jennifer call a taxi from there to get home. ^[1] To save time, they cut across the railroad tracks instead of following the streets. ^[1]

On the tracks, the girls first passed Roman and Frank Sandoval. That encounter came to nothing; the brothers let them go by without incident. ^[1]

Farther along, the girls crossed paths with other members of the gang. As they moved past Joe Medellin, he suddenly grabbed Elizabeth and dragged her down a hill as she screamed for help. ^[1] Jennifer ran back toward her friend, but Cantu grabbed her and pulled her down the hill as well. ^[1]

At that point, the Sandoval brothers decided to get out. Cantu asked if they wanted to “get some,” but Roman replied that he did not rape or kill girls, and the brothers left. ^[1]

Assaults on the tracks and a decision to kill

With the Sandovals gone, the remaining gang members turned on Jennifer and Elizabeth. According to later boastful statements recounted in court, they committed a gang rape of both girls. ^[1] Fourteen‑year‑old Venancio watched as the assaults unfolded. ^[1]

Cantu pressured the younger boy to join in, telling him he should “get some.” ^[1] As the crimes continued, Cantu leaned in and whispered another message to the teenager: “We’re going to have to kill them.” ^[1]

When the assaults ended, Cantu told the others to take the girls into nearby woods. ^[1] There, according to the evidence, the group proceeded to strangle both Jennifer and Elizabeth. ^[1] Cantu kicked Elizabeth in the face with his steel‑toe boots, knocking out several of her teeth. ^[1] He then stepped on Jennifer’s neck until she stopped moving, and the group took turns stomping on both girls’ necks to make sure they were dead. ^[1]

Weeks later, when the bodies were finally discovered, decomposition was so advanced that dental records were the only way to confirm the remains were Jennifer Ertman and Elizabeth Peña. ^[1] The medical examiner’s finding—that both died from neck trauma consistent with strangulation—matched the story that emerged in the courtroom. ^[1]

A night of bragging at the Cantu house

What happened next shifted the case from whispered rumor to a prosecutable crime.

Later that night, Cantu, Medellin, Perez, and Villareal regrouped at Cantu’s house. ^[1] Cantu walked in as the others were recounting what they had done to his older brother, Joe Cantu, and Joe’s wife, Christina. ^[1] The conversation, described in trial testimony, was graphic. ^[1]

According to Christina, Cantu seemed happy and amused as he listened and chimed in. ^[1] When his co‑defendants described particular acts, he agreed and punctuated the stories with phrases like “I did that” and “yeah, I did that, too.” ^[1] Christina recalled that Cantu, Joe, a man identified as Junior, and Raul all said, “we had to kill them.” ^[1]

The boasting was not just talk. Cantu divided up jewelry and money taken from Jennifer and Elizabeth, handing pieces out in his bedroom. ^[1] Later, investigators would recover most of the victims’ jewelry, including some from that room. ^[1]

Christina eventually convinced Joe that they could not stay silent. She urged him to report what he had heard to police. ^[1] That decision became the first major crack in the gang’s wall of secrecy.

Bodies, evidence, and a tightening net

Once police were alerted, the investigation widened quickly.

By the time searchers located the bodies, decomposition had erased many identifying features. Dental records confirmed that the remains belonged to Jennifer Ertman and Elizabeth Peña. ^[1] The medical examiner concluded both girls had died as a result of trauma to the neck consistent with strangulation. ^[1]

Detectives traced the crime back to the Black and Whites. Eventually, all individuals who had participated in the gang rape and murders were arrested. ^[1] Most of the girls’ stolen jewelry was recovered; some of it was found in Cantu’s bedroom, corroborating Christina’s account of him passing it out after the attack. ^[1]

The forensic picture was reinforced by statements from within the group. Cantu gave two confessions. ^[1] In addition, the trial court admitted out‑of‑court statements made by the young men in each other’s presence—statements that described the assaults and killings—as adopted admissions by Cantu. ^[1] The court also held that these statements qualified as declarations against penal interest, supported by corroborating evidence such as Cantu’s responses, the possession of the victims’ jewelry, and blood found on co‑defendants’ clothing. ^[1]

Against that backdrop, Derrick Sean O’Brien appears in the record as one of the named members of the Black and Whites present at the initiation that set the night in motion. ^[1] His name is part of the constellation of young men whose actions, words, and presence shaped what happened on and around those tracks.

The capital case against Peter Anthony Cantu

Prosecutors charged Cantu with capital murder for killing Jennifer Ertman while committing, or attempting to commit, robbery, kidnapping, and aggravated sexual assault. ^[1] He was tried under the 1992 version of Texas Code of Criminal Procedure Article 37.071, the state’s capital sentencing statute. ^[1]

In February 1994, a jury convicted him of capital murder. ^[1] Under Texas law, that verdict triggered a second phase of the trial focused on punishment, structured around special issues—including whether the defendant would likely pose a future danger. ^[1]

The jury answered those questions in a way that allowed the maximum penalty. Based on their answers to the special issues in Article 37.071 §§ 2(b) and 2(e), the trial judge sentenced Cantu to death. ^[1] Direct appeal to the state’s highest criminal court followed automatically, as required by Article 37.071 § 2(h). ^[1]

On appeal, Cantu did not challenge the sufficiency of the evidence to support the jury’s guilty verdict. ^[1] Instead, he attacked the punishment decision, arguing among other things that the evidence was insufficient to support the jury’s finding that he would be dangerous in the future. ^[1] In total, he raised forty‑five points of error. ^[1]

The appellate opinion gives a window into how the trial unfolded:

• Cantu sought jury instructions explaining parole law, but the court cited prior Texas cases and held that such instructions are not required in capital cases. ^[1]
• He moved for funds to hire an expert to study jurors’ understanding of the special punishment questions. ^[1] The court ruled he had not shown a particularized need and denied the request. ^[1]
• His lawyer challenged the admission of co‑defendants’ out‑of‑court statements—those late‑night boasts at the Cantu house—on hearsay and confrontation grounds. ^[1] The appellate court upheld their admission as adopted admissions and statements against interest, backed by physical evidence. ^[1]
• At punishment, the defense called fifteen‑year‑old Beatrice Martinez, who said she had known Cantu for about three years and that he was friendly and had never mistreated her. ^[1] On cross‑examination, the State introduced letters she had written to Efrian Perez, including a vulgar passage mocking the victims, to suggest bias and impeach her credibility. ^[1] The trial judge allowed the questioning, and the appellate court agreed it was proper impeachment. ^[1]

The rest of the gang in the shadows

While Cantu’s name anchors the appellate opinion, the case file never truly stands alone. It is threaded with other figures whose roles range from central to peripheral.

Derrick Sean O’Brien is one of the people the record places at the initiation meeting on June 24, 1993, when the Black and Whites welcomed Raul Villareal and then drifted toward the railroad tracks. ^[1] The same narrative that details the assaults and killings names O’Brien as a member of that circle, even though this particular slice of the legal history does not spell out his charging or sentencing outcome. ^[1]

Others are easier to trace on paper, if not in detail. Texas prison records list an inmate named PEREZ, EFRAIN—race Hispanic, male, age 50—serving a life sentence at the Wynne Unit, with both maximum sentence and projected release fields marked “LIFE SENTENCE.” Another entry shows VILLARREAL, RAUL OMAR—also Hispanic, male, 50—held at the Beto Unit, likewise under a life sentence.

The records do not, in this excerpt, spell out which convictions led to those imprisonments. They do, however, underline a basic reality: for at least some of the young men named in the Jennifer Ertman and Elizabeth Peña case, the consequences ultimately stretched across decades.

Remembering Jennifer Ertman and Elizabeth Peña