Deputies found the 18-year-old's body on Dec. 2 at a mobile home at 4221 Olive Branch Lane in New Hill after receiving a tip from Apex police.
Hare, Shaw and Dahlquist were also indicted on one count each of conspiracy to commit murder.
According to the warrants warrants, one of the accused confessed to being involved in Silliman death and implicated three others. Of the other three, two more confessed to their involvement. The three who confessed implicated the fourth suspect as being directly involved in his death.
One of the suspects admitted to beating Silliman on the head with a hammer, tying him with zip ties, suffocating him with duct tape and disposing of him in a plastic bag, the warrants stated. The suspect also told investigators they tried to use medication commonly used for animals to plan the crime.
Dahlquist and Khan are seniors at Apex High School, a Wake County schools spokesman said. Shaw is a sophomore at Panther Creek High School in Cary. Hare withdrew from Panther Creek in February.