13 members of the MS-13 gang were indicted Thursday on seven killings on Long Island spanning three years, including the deaths of several high school students last year. The US Attorney’s Office for the Eastern District of New York said the Ms-13 members of “La Mara Salvatrucha” face offenses including seven murder charges, racketeering, attempted murder, assault, obstruction of justice and arson in the 41-count indictment Thursday in federal court in Central Islip, New York.

Two of the students, Nisa Mickens, 15, and Kayla Cuevas, 16, were beaten with baseball bats and a machete. Both girls attended Brentwood High School in Brentwood, Long Island. At the time, police said there appeared to be gang involvement in the girls’ deaths and the deaths of two others, whose skeletal remains were found after they had been missing for months. Police have not announced arrests in the latter two deaths.

Kayla was involved in a “series of disputes” with MS-13 gang members and associates months earlier, authorities said. She and friends then became involved in an altercation at Brentwood High a week before the girls’ deaths, authorities said. MS-13 members vowed to seek revenge.

According to authorities, on September 13, gang members went looking for rival gang members to kill in Brentwood. The girls had gone for a walk that night and they recognized Kayla, and got permission to kill the girls from two gang leaders. All three members have been indited.

A passerby found Nisa’s body on a Brentwood street on September 13 and the next day, Kayla’s body was discovered in the backyard of a nearby home. Authorities said a third Brentwood High School student, Jose Pena, 18, was killed on June 3, 2016. His skeletal remains were discovered on October 17, 2016, in a wooded area that served as a burial ground for MS-13 victims. Pena was killed because he was suspected violating gang rules, federal authorities said.