The scene where the body of Jholie Moussa was found in Woodlawn Park in the Mount Vernon area. (Justin Jouvenal/TWP)

A 17-year-old from the Alexandria, Va., area is a person of interest in the killing of Fairfax County teenager Jholie Moussa, whose body was found in a Mount Vernon-area park Friday, police said Tuesday.

The teenager, who was not identified because he is a juvenile, has not been charged in Jholie's slaying, but he is facing a count of felony assault in relation to an attack on the 16-year-old before she disappeared Jan. 12.

The assault was previously unreported, and police uncovered it as they searched for Jholie, who went missing after leaving her Mount Vernon-area home two weeks ago. The 17-year-old was arrested Jan. 18 in the assault.

Fairfax County police declined to go into detail about the relationship between the boy and Jholie. They also declined to reveal the nature of the assault because the case involves a juvenile.

At a news conference Tuesday evening, Fairfax County police Maj. Rich Perez defended the department's handling of Jholie's case. The teen's family has criticized the department's handling of the matter. Family members said they thought the police did not approach the disappearance with urgency.

"Every resource necessary has been and will be deployed," Perez said.

Fairfax County police officers found Jholie's body covered in leaves and debris in Fairfax County's Woodlawn Park on Friday morning. Perez declined to say what prompted police to go to the park, which they had searched on Jan. 20 and is less than a mile from Jholie's home.

Jholie's mother said in a Facebook post that the family last saw the teenager leaving home, in the 4200 block of Sonia Court, about 4:15 p.m. on Jan. 12. The post said Jholie told her sister she would be right back but did not return.

About 8:02 p.m., Jholie's sister received a text message from Jholie's phone saying that Jholie was going to a party in Norfolk. That was the last time members of her family heard from her. Alexandria and Norfolk are about 190 miles apart by road. The family reported Jholie missing the next day.

Cyrille Moussa, Jholie's father, told WUSA9 television that Jholie received a call on Jan. 12 from a 12-year-old boy's cellphone. The father said the boy later told him a man asked to borrow his phone to place the call.

Perez would not confirm that account and would not say whether the man who used the boy's cellphone was the 17-year-old.

Police have not offered a motive for the slaying or explained how Jholie was killed. Also unclear is how long she was dead before police found her body. Perez said an autopsy in the case is pending.

Fairfax County police said last week that they had interviewed about 20 of Jholie's friends but that many were not cooperating.

Fairfax County police 2nd Lt. James Bacon said at the news conference Tuesday that Jholie left home under circumstances that did not appear to be unusual, so there was no reason to think she had been abducted or was in danger.

Jholie disappeared on a Friday. By the following Tuesday, police decided to upgrade her status to endangered because she had not posted to social media or had other electronic contact with anyone close to her. Police said they followed up numerous leads in the case, as far away as Philadelphia.