Daniel Ramos, left, and Juan Espinal Rapalo. Luis Avelar Morales and Edwin Reyes-Martinez were not adults at the time of the murder and their mugshots are not being released. (Montgomery County Police Department)

Four Montgomery County teenagers were charged in the brutal stabbing and beating of a 34-year-old man whose body was found in a shallow grave four months ago — the latest in a series of local killings that police say are tied to a resurgence of the MS-13 street gang.

The victim, Marvin Vargas-
Osorio, was lured to the already-made grave in the Germantown area of the county, according to District Court documents filed Wednesday. As many as five assailants stabbed Vargas-Osorio — two doing so from the back — and continued attacking after he fell to the ground, the documents state. Two of the assailants then put his body in the grave.

Of the four teens arrested so far, three allegedly wielded knives, while the fourth acted as a lookout. Edwin Reyes-Martinez, who is suspected of being the lookout, is an 18-year-old student at Gaithersburg High School. He was the first of the suspects to have a hearing in the case.

At approximately 5-foot-3 and 130 pounds, Reyes-Martinez appeared on a video monitor from the county jail on Wednesday afternoon. He is charged with first-degree murder.

“He is an active participant in the violent gang known as MS-13,” prosecutor Teresa Casafranca said in court. “He absolutely poses a risk to the public — anyone he may come in contact with.”

District Court Judge John C. Moffett ordered Reyes-Martinez held without bond.

According to court papers and police officials, all four suspects also have been charged in connection with another slaying that occurred in early November. In that case, the victim — Roberto Cruz, 22 — was lured into a wooded area in Gaithersburg, where he was ordered to his knees and shot, according to police. Detectives earlier alleged that the shooter said he’d killed him “on behalf of” MS-13.

In recent months, law enforcement officials have spoken out about a resurgence of MS-13, the region’s biggest and most notorious gang.

“MS-13 has never gone away. But we haven’t seen this level of violence in several years,” Capt. Darren Francke, commander of the Montgomery Police Department’s major crimes division, said Wednesday. “We are focused on bringing every involved member to justice.”

“MS-13 appears to be making a push for recruitment, once again reverting to their old tactics of violence and intimidation,” Douglas Keen, chairman of the Northern Virginia Regional Gang Task Force, said last month.

Police identified the other three suspects in the recent slayings as Luis F. Avelar Morales, 18, Daniel Adonai ­Ramos, 19, and Juan Espinal ­Rapalo, 18. Jail officials said Wednesday that immigration agents have lodged detainers against all three — an indication they are believed to have entered the country illegally. No detainer had been lodged against Reyes-Martinez as of Wednesday.

Authorities are still trying to learn more about the motive. Two law enforcement officials said that it does not appear that
Vargas-Osorio was a gang member. Court records outline how detectives had been working on the Cruz killing when they got a break in the Vargas-Osorio case.

In November, after the killing of Cruz, detectives apprehended and interviewed Rapalo, who is suspected of being a member of MS-13. He said he had been in the woods the night Cruz was shot, heard an associate order Cruz to his knees, heard the shots, and saw Cruz fall forward, according to the charging documents.

Rapalo said the same associate “caught up to him and gave him a gun to hide,” detectives wrote. Rapalo did so, but later went back, retrieved the gun, and moved it “deeper into the woods,” detectives wrote. ­Rapalo said he did so with two others. Rapalo agreed to take the detectives to the gun, and they found it.

Detectives began talking to another witness linked to that gun, and their conversation turned to the body that had been found in a shallow grave.

By that time, detectives had been making progress in the case — which began after hunters found the remains on Aug. 29 at Great Seneca Stream Valley Park, which is in the Germantown-Gaithersburg area.

Investigators, assisted by a forensic anthropologist, learned the victim had been stabbed in the head and upper body, and had been beaten in the head. “The scene was consistent with a gang-style murder,” detectives wrote.

The witness said he knew the victim by his nickname, ­“Mango,” and that Mango was a friend of his family’s.

He told detectives that he was at the park the day that Mango was killed. He said that as many as five others were there. He told police that the group began stabbing Vargas-Osorio, some coming at him from behind.

A lawyer from the public defender’s office told the judge that Reyes-Martinez lives with his mother and four younger siblings. He has no criminal history and has worked summer jobs to help support his family, the lawyer said.