Here is what you need to know about MS-13, a street gang with an international reach. (Claritza Jimenez/The Washington Post)

Carlos Otero Henriquez told a friend he was a member of the 18th Street gang. On Facebook, he posted photos of himself flashing his gang’s signs. When members of the rival MS-13 gang noticed, the 18-year-old from Leesburg, Va., was targeted for murder.

“We’re always patrolling the area to make sure it’s clean of enemies,” Wilmar Javier Viera Gonzalez, a top Virginia MS-13 leader recently testified in Alexandria federal court. He showed jurors a notebook he kept full of MS-13 codes, nicknames and rules. Among the gang’s policies: To move up, “you must kill a rival.”

Before his arrest, Viera Gonzalez commanded a Northern Virginia chapter of MS-13 called Virginia Locos Salvatrucha and was in charge of the state for a larger group called the “East Coast Program.”

Now he has testified against six former subordinates, joining two other MS-13 members involved in the murder who hope their cooperation will get them out of prison before their own deaths. The trial is expected to conclude this week.

MS-13 graffiti marks a highway bridge in Springfield, Virginia. (Michael Miller/The Washington Post)

In court last week, Viera Gonzalez, who formerly held the title “first word” of the VLS, calmly admitted he ordered members of his gang to stab Henriquez to death in May 2016 so they could rise up the ranks.

“He had no idea that night would be his last,” Assistant U.S. Attorney Patricia Giles said of Henriquez in her opening statement. “He had no idea of the horrible death he would suffer.”

The criminal case is among several playing out across the D.C. region involving violence attributed to MS-13, which had a resurgence in the area and other parts of the country in recent years.

In the Alexandria federal court case, the members of the VLS chapter had learned through an associate that Henriquez was in the 18th Street gang, which has battled MS-13 in the United States and El Salvador for decades. “If he was [18th Street], we must kill him,” Viera Gonzalez said.

It was an MS-13 hanger-on named Andres Velasquez Guevara who alerted the gang members to the rival, according to court documents. He had become friends with Henriquez early in 2016. Early on, Velasquez Guevara later told police, he asked his new friend if he was in a gang.

Henriquez said yes: 18th Street.

“Here, you don’t go around saying things like that,” Velasquez Guevara told police he responded. “Dangerous.”

When he became friends with Henriquez on Facebook in April, he saw the teenager had posted photos of himself making 18th Street gang signs. He passed those photos on to Miguel Gomez, an MS-13 member, according to court documents, who alerted gang leaders in El Salvador.

The message came back to kill Henriquez, Viera Gonzalez said.

Soon after, as the gang members were planning to go to a club, second-in-command Dublas Lazo got a call from Velasquez Guevara. He was with Henriquez.

The victim was brought to a van, where MS-13 members waited.

“He was told that we were going to a party . . . where there were girls,” testified Manuel Antonio Centeno, who has also pleaded guilty.

As they drove, Viera Gonzalez said he turned the music up and discussed with the driver where they might kill Henriquez undetected.

They decided on the isolated mountains of West Virginia. On the way there, Viera Gonzalez passed around Heinekens and asked Henriquez questions: Where he was from, how long he had been in the country and whether he was in a gang.

Henriquez said he was in the 18th Street gang. He asked Viera Gonzalez the same questions, noting his tattoos and that he was from San Miguel, a city in El Salvador dominated by MS-13.

No one in this van is in a gang, the MS-13 leader said he responded.

Eventually they stopped at a gate to a park and got out. Lazo stayed by the van as a lookout. The others walked down a gravel path.

“Why are you guys waiting to light it up?” Viera Gonzalez asked.

That was the signal. They surrounded Henriquez and told them they were MS-13.

“I kind of figured something crooked was going on,’” Viera Gonzalez recalled Henriquez saying.

The gang leader and Centeno watched and filmed while four others beat Henriquez, Viera Gonzalez testified.

“They had to do jobs” to become full MS-13 members, Centeno testified through an interpreter. “To assassinate someone — that is a job.”

When Henriquez tried to stumble to his feet, Centeno testified, he hit him with an empty beer bottle.

Viera Gonzalez said he told the four to each grab Henriquez by a limb. He approached, while Centeno recorded with his phone and shone a flashlight in the teenager’s face.

“I said, ‘I promise, if you provide us with information, we’re not going to kill you,’ ” Viera Gonzalez recalled. “He refused. He said he was going to die for it.”

Henriquez grabbed his leg. Viera Gonzalez kicked him in the face.

“I told them to finish it,” he testified. “They all took a chance, one at a time, stabbing Carlos with the pocketknife.” He was stabbed in the stomach so many times, Viera Gonzalez said, “you could see his intestines.”

Viera Gonzalez told them to make sure Henriquez was dead, so he said one gang member stabbed the victim in the throat. Centeno took pictures to send to leaders in El Salvador, he said. Then they stripped Henriquez, threw his body in a ditch and set his bloody clothes on fire.

“When his body was recovered, it was mostly bones,” Giles told jurors.

As they walked back to the van, Viera Gonzalez said, they all put their hands in the air and made an MS-13 sign.

As Henriquez’s mother searched for her son, Giles said, she found clues that helped police track the conspirators down.

Unbeknown to the others, at the time of the murder Lazo had already been cooperating with the FBI to expose suspected extortion, defense attorney Robert Jenkins said in court. Lazo had even filmed his fellow gang members demanding “rent” from a young man.

Lazo initially denied involvement in the murder but took police to the body.

Now he faces a mandatory life sentence if convicted, as does Daniel Flores-Maravilla, Carlos Jose Benitez Pereira and Lelis Ezequiel Treminio-Tobar. Velasquez Guevara is charged only with helping kidnap Henriquez, and Juan Carlos Guadron Rodriguez with involvement in the extortion plot.

Although murdering rivals is how MS-13 members advance, Viera Gonzalez said he was not actually interested in killing Henriquez. It was Gomez who pushed for the murder, he said, and was the first to stab Henriquez.

“If there was any way I could have stopped it, I would have,” Velasquez Guevara later told FBI agents.

Yet Gomez, who also testified at trial and has pleaded guilty in the case, was the first to cooperate with prosecutors. He disappeared after the murder, and the clique nearly had him marked for assassination. But he got back to a fellow gang member that day, Viera Gonzalez said, to say he just needed some time alone.

“Not everybody’s of a strong mind about what happened with Carlos’ murder,” Viera Gonzalez testified he thought at the time. “Not everybody can live with it.”