sergio, was one of the two victims. the other young man killed, 17-year-old edmond escobar mendez. these just unsealed court documents reveal why the teens were targeted. mendez disappeared in late august. his family reporting him missing days later. then in late september, facebook information led his brother to seek out a friend, sergio tremenio. he gave him bad news saying he had been abducted or killed because ms-13 members thought he was a spy for a rival gang. just two days later, on september 27th, tremenio also disappeared. his worried mom contacted police to report him missing. then in december, new information. detectives learned the teens had been killed and members. but it wasn't until february they got the tip that led them to this wooded burial ground. >>> now, since then the fbi has taken over this case. so, when any charges do come, they will be in federal court. no word yet on whether any arrests have been made. it is likely if there have been indictments at this point, they are still under seal. reporting live from fairfax county, i'm julie carey. >> scott macfarl