A man was beheaded and had his heart ripped out by a gang before they buried him in a park near Washington DC, police have said.
The unidentified victim was stabbed more than 100 times by up to 10 suspects who communicated on walkie talkies while closing in on him in Wheaton, Maryland.
An informant led police to a makeshift grave in Wheaton Park in September.
Newly revealed court papers reveal the man had his head and heart removed during the attack, which is said to have taken place in the spring.
An alleged member of the MS-13 gang, Miguel Angel Lopez-Abrego, 19, has been arrested on first-degree murder charges.
Montgomery County Police Department is searching for more suspects.
The gang is accused of luring the victim to the park, where his grave had already been prepared.
No motive has been established – but police think the attack was planned over two weeks.
MS-13, also known as Mara Salvatrucha, is estimated to have 10,000 members across the US.
The gang contains small units, known in Spanish as "clicas", with some larger and more violent than others.
US President Donald Trump has made the gang's elimination a focus of his crackdown on crime.
He claims crime has surged as a result of gang members being easily able to cross borders.
The majority of members are originally from El Salvador, Honduras or Guatemala, with as many immigrants in the gang as there are US citizens.
Last week US authorities said they had picked up 214 MS-13 members during a month-long nationwide sweep led by the Immigration and Customs Enforcement Agency.
More than half were arrested on immigration offences.
A total of 93 were charged with criminal offences, including murder, robbery, racketeering and drugs.