More than a dozen members of the notorious MS-13 gang were indicted for seven murders in Long Island, including the grisly killings of three high school students last year.

The 13 alleged gang members - ten of whom are undocumented immigrants - face seven murder charges, racketeering, attempted murder, assault, obstruction of justice and arson in the 41-count indictment.

They include Jairo Saenz, 19, a leader of one of the local factions of MS-13 called Funny, and his older brother Alexi, 22, leader of another MS-13 associated gang named Blasty.

Two of the victims were best friends Nisa Mickens, 15, and Kayla Cuevas, 16, who attended Brentwood High School in Suffolk County, New York City.

The girls were beaten to death with baseball bats and hacked with machetes after they went for a walk together on September 12. Their bodies were found over the next few days.

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Law enforcement officers take one of the suspected MS-13 street gang members into custody in Central Islip, New York Thursday, as more than a dozen members are charged with murdering high school students

The skeletal remains of a third Brentwood High School student, Jose Pena-Hernandez, 18, was discovered the following month on the grounds of an abandoned state psychiatric hospital - a quiet wooded area that had served as an unofficial burial ground for the gang's victims.

Police say Pena, who was murdered on June 3, 2016, showed evidence of 'repeated stab wounds and beatings with a bat, a blunt force instrument.'

'Law enforcement was determined that these brutal murders wouldn't turn into cold cases,' US Attorney Robert L. Capers told reporters.

Pena was an alleged MS-13 gang member who was lured to the grounds of an abandoned state psychiatric hospital by fellow gang members he thought were his friends, Capers said. Those friends turned on him and repeatedly stabbed him to death, he said.

Nisa Mickens, 15, (left) Kayla Cuevas, 16, (right) from Long Island, New York, were were ambushed by a carload of other teens on September 13 and killed. Thirteen members of the MS-13 gang were arrested on Thursday in connection with the slayings

A poster shows pictures of two of the slain teenagers and an offer of a reward

His death had gone largely publicly unmarked until police began discovering corpses in the weeks after Cuevas and Nisa died.

Eleven gang killings in Suffolk County last year were attributed to MS-13. Some people complained that police, school officials and others were not doing enough to stem the violence.

Since then, police have arrested more than 125 suspected MS-13 gang members in Brentwood and elsewhere.

Two other killings of Brentwood youths, ages 15 and 19, whose bodies were discovered last year in secluded spots in the hamlet, remain unsolved.

In the case of the two high school girls, Robert L. Capers, the United States attorney for the Eastern District of New York, told the New York Times how Kayla had been 'feuding' with gang members at school and on social media.

She and her friend Nisa, who was simply 'at the wrong place at the wrong time' were walking along the street at around 8.30pm when Selvin Chavez and Enrique Portillo, both 19, along with two juvenile gang members, were cruising in a car, Capers said.

Capers said the MS-13 members spotted the girls and called the Saenz brothers who reportedly gave the order to kill them.

They attacked Nisa first, beating her so brutally with baseball bats and machetes that her body was unrecognizable.

Kayla 'ran for her life' and even made it into the nearby woods before the gang members caught up with her and murdered her.

Evelyn Rodriguez, mother of Kayla Cuevas, 16, stops to talk members of the press gathered outside U.S. District Court Thursday, March 2

'This was the worst I had ever seen,' Sini said of the crime scene.

Gang violence has been a problem in Brentwood and some surrounding Long Island communities for more than a decade, but Suffolk County police and the FBI began pouring resources into a crackdown after the killings of the high school girls sparked outrage.

'While violence and brutality are trademarks of the MS-13 gang, the murders of these three teens are particularly disturbing,' U.S. Attorney Robert Capers said in announcing the indictment Thursday.

Cuevas was targeted last summer by a group of four gang members, including two juveniles, because she had been feuding with MS-13 members at school and on social media. The posse, which had been roving in a car looking for gang enemies, attacked when they came across her walking with Nisa in the street.

'(Nisa) Mickens was simply at the wrong place at the wrong time, hanging out with her childhood friend,' Capers said.

Robert Mickens, Nisa's father, said he felt blessed that police had made arrests.

'I've got some type of closure even though my daughter is not back. It's closure to my family,' he said.

The indictments came as two members of the same gang, based in Houston, were charged on suspicion of killing one teenager and kidnapping of another, authorities said.

WHO IS THE FEARED MS-13 GANG? The ultra-violent street gang MS-13 was the first to be designated as an international criminal group. The gang was founded by immigrants fleeing El Salvador's civil war more than two decades ago. Its founders took lessons learned from that brutal conflict to the streets of Los Angeles and built a reputation as one of the most ruthless and sophisticated street gangs, according to Immigration and Customs Enforcement Special Agent Jason Shatarsky. With as many as 10,000 members in 46 states, the gang has expanded far beyond its initial roots. Members are accused of major crimes including murder, kidnapping, prostitution, drug smuggling and human trafficking. The group's violence — using a machete to hack a victim to death or shooting someone in the head in broad daylight, for instance — surprised authorities and even rival gangs. 'They saw a level of violence that hadn't been seen before,' Shatarsky said, adding that as the gang has expanded it has also become more sophisticated than many rivals. The gang, which is allied with several of Mexico's warring drug cartels, has a strong presence in Southern California, Washington and Northern Virginia, all areas with substantial Salvadoran populations. Among the most high-profile killings attributed to MS-13 in Virginia was the 2003 slaying of a pregnant teenager who had become an informant. Brenda Paz, 17, was stabbed to death and her body was left along the banks of the Shenandoah River. One of Trump's priorities is a crackdown on immigrants who are in the country illegally and have committed crimes. He promised as much in his December interview with Time magazine, when he referenced a Newsday story about the killings. 'They come from Central America. They're tougher than any people you've ever met,' he said. 'They're killing and raping. Advertisement

Gang leader Miguel Angel Alvarez-Flores, 22, who also goes by 'Diabolico,' and 18-year-old Diego Alexan Hernandez-Rivera, who had a Satanic shrine in their Houston apartment, laughed, smiled and waved in court as they faced charges of aggravated kidnapping and murder.

Prosecutors said the two kidnapped a 14-year-old girl after she left school around February 2, holding her in an apartment where she was raped by a gang member.

After four days, the girl said she was taken to a different apartment where six gang members lived, and Flores kept a makeshift Satanic shrine.

Authorities say she was held against her will there for two weeks, given drugs and alcohol to keep her disoriented, and sexually assaulted by some of the men.

She also said she was held down while Flores tattooed a giant grim reaper from her knee to her foot, the Houston Chronicle reported.

She told investigators that a second girl she only knew as 'Genesis' also was held at the apartment. That girl was found shot dead in the head and chest on February 16, and has not yet been identified.

The killings came amid a national conversation about illegal immigration, and prosecutors revealed in a news conference that 10 of the 13 indicted suspects were citizens of El Salvador or Honduras who were in the U.S. illegally, including most of the people directly implicated in the murders.

Last December, Donald Trump referenced the killings in Brentwood during a profile for his Time magazine 'Person of the Year' award after being elected president.