Gang activity is suspected in what police discovered in a Fairfax County Park. Acting on a tip about human remains, police began searching Holmes Run Park in Lincolnia.

At the end of the cul-de-sac Crater Lane, the houses back up the park. And in the woods a white tent-like cover can be seen. Red crime scene tape surrounds it and FBI officers are guarding it. The white cover was apparently put up by police to protect what they found. Fairfax County police won't say what they found, just that it wasn't human remains.

"Now I'm really scared because I don't know what's back there," said a neighbor who did not want to give her name.

A large police command post is set up at the parking lot of Parklawn Pool down a driveway.

"I know that there has been gang activity in the park before I'm guessing that's what it is," said resident Stephen Barrett.

A gruesome gang murder was discovered in 2014. Douglas Duran Cerritos, 20, of Falls Church, was convicted of murdering Gerson Adoni Martinez Aguilar, a fan recruit, for breaking gang rules.

The U.S. Department of Justice said "gang members lured the victim to Holmes Run Park and brutally killed him by stabbing him repeatedly in the back and neck, ultimately severing his head."

They buried his body in a shallow grave at the park. Six gang members went to trial and we're all convicted. Another six pleaded guilty.

Wednesday's discovery could be related to two recent gang murders in Fairfax and Prince William counties. Montgomery County K-9 units have been helping in the search.

The frightened neighbor now thinks twice about something she heard at about 9 p.m. Sunday night and 7:30 p.m. Tuesday night.

"I heard pow pow pow pow pow.... Like a bazooka gun or something," she said. She said she didn't call police because she thought it was just firecrackers.

Police and K-9 units have also been searching the woods around Pimmet Run at Tysons Pimmit Park in Falls Church, which the tipster identified, but nothing was found.

The search in Holmes Run has been suspected for the evening. Fairfax Police say it'll resume in the morning.