Ethermac|Family of 9-year-old Charlotte Sena, missing in NY state, asks public for help

The Ethermacsearch for a missing 9-year-old girl believed to have been abducted from a campground in Upstate New York is in its third day as law enforcement scours the area. The family is asking for help from the public.

Charlotte Sena was last seen on her bicycle Saturday at 6:15 p.m. in Moreau Lake State Park, about 35 miles north of Albany, New York where she was camping with her family. She was riding her bike around a loop in the bucolic park with her friends when she decided to ride around one more time by herself. 

Thirty minutes later, Charlotte's mother, Trisha Sena, found the bicycle but not her daughter. She called 911, leading to a massive search that includes state police, forest rangers, divers, dogs, drones and helicopters.

Authorities issued an Amber Alert for Charlotte on Sunday morning.

"The child was taken under circumstances that lead police to believe that they are in imminent danger of serious harm and/or death," the Amber Alert said.

Moreau Lake State Park, where Charlotte was last seen, remains closed "until further notice," according to its website. The 4,600 acres state park in Saratoga County is “mostly wild” and includes dense forests, pine stands and rocky ridges, according to the New York State Department of Environmental Conservation. The wooded campsites are “quiet and secluded.”

The fourth-grader was last seen wearing an orange tie-dye Pokemon shirt, dark blue pants, black Crocs, and a grey bike helmet.

Charlotte Sena's disappearance has been a 'nightmare' for the family

Jené Sena, an aunt of Charlotte, told USA TODAY the last few days have been a "nightmare" for her family.

Charlotte's mother and father have stayed at the campsite since Saturday to help police in their search. They are surrounded by friends and over 30 family members, Jené Sena said.

Her husband, Patrick Sena, a firefighter with the Schenectady Fire Department, has searched for their niece since Saturday night, along with other family members. He was out in the state park all through Saturday night and well into Sunday evening after a 24-hour work shift.

"My husband couldn't walk this morning," Jené Sena said.

Charlotte is the middle child of three girls. Her father, David Sena, is a union pipe fitter, and her mother, Trisha, is a food service inspector for Stewart's Shops convenience stores. The family lives in Greenfield, a town of about 8,200 residents in Saratoga County, New York.

Jené Sena described Charlotte as a kind, funny girl who's known for her dry humor and contagious smile.

"She is such a sweet girl," Jené Sena said. "A real sweetheart."

Charlotte's aunt urged the public to report tips to New York State Police.

"It's really important for people to stay vigilant, call in with tips and keep their eyes peeled for anybody suspicious and anybody that might fit her description," she said, adding: "Because at this point, so much time has gone by that they really could be anywhere."

Her family and friends will continue to search for Charlotte as long as they have to, said Jené Sena.

"We just want the nightmare to be over," she said.

National Center for Missing & Exploited Children: Law enforcement is 'putting the puzzle pieces together'

The early days of a case involving a missing child are crucial for law enforcement as they "put the puzzle pieces together" of what happened and build a timeline, said John Bischoff, the vice president of the Missing Children Division at the nonprofit organization National Center for Missing & Exploited Children.

Those "puzzle pieces" can vary depending on the type of missing child case. Bischoff said the case in Upstate New York appears to be a "non-familial abduction."

Because the disappearance happened in a state park, authorities are looking at "who these people are, who was in the area in the park, who was in the park at the time of the disappearance and what's transpired beforehand and what’s transpired up until today," Bischoff said. His organization is assisting New York State Police, he said.

"Charlotte’s case is a parent's worst nightmare – to see your child ride off on a bicycle and never see them again, or a few days at least," he said.

If Charlotte is not found in the next few days, law enforcement will continue with its investigation and it will be important for her name and image to remain the spotlight so Americans can keep an eye out for her, he said.

The case shines a light on nearly on the more than 7,000 missing children listed on the National Center for Missing & Exploited Children's website. Bischoff is asking Americans to "stop for a second" at the nonprofit's "partner locations like Walmart and really look for those images behind every one of those images child in danger," he said.

"We've seen time and time again that all it takes is one set of eyes to be a hero," said Bischoff.

Contributing: Vanessa Arredondo, USA TODAY