TAMPA — The search for 17-year-old Hailey Acierno ended sadly Friday, in a corner of the sprawling wilderness park where the Wharton High School junior found respite from a sometimes overwhelming world.

Tampa police officers on off-road bicycles discovered Hailey's body shortly before 9 a.m. off the main bicycling and hiking trail south of the Morris Bridge Road entrance to Flatwoods Park. She was found about two miles south of her house in the Arbor Greene subdivision, where she was last seen on March 28, Police Chief Eric Ward said at a news conference.

Investigators believe the girl, who has bipolar disorder, took her own life, Ward said. The medical examiner will confirm the cause of death and estimate how long she had been dead.

"It's a very tragic incident," Ward said, asking for privacy for Hailey's family. "Our thoughts and prayers are with them."

The discovery ended an intense search that began 11 days earlier, when Hailey's mother Lisa Acierno returned home from work to find Hailey gone. Hailey's loved ones had been especially concerned about her welfare because she was supposed to be taking medication.

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That morning, Lisa told the Tampa Bay Times on Thursday, Hailey was lingering in bed despite warnings from her mother that she couldn't be late for work. Hailey's father Chris had already left. When Hailey remained in bed, Lisa took her phone as punishment and left.

She returned to find Hailey's bed made and the dishwasher empty. That seemed to indicate she hadn't run away, Lisa said.

She described her daughter, the youngest of three, as sweet and kind, the type who urges her to catch and release, rather than squash, bugs that found their way into the house. But without her medication, she had "very, very highs and very, very lows" that could spark fits of uncontrollable crying and hobble her ability to form complete sentences.

Lisa looked in the places her daughter could often be found: the neighborhood community center, the library and the nearby Domino's Pizza. Then she called police.

Investigators immediately focused on the 5,500-acre Flatwoods Park. The tract's northern boundary is just steps away from the Aciernos' home and Hailey would often walk into the woods with friends or family or by herself. She loved capturing the park's natural beauty on her Canon camera, her mother said. Investigators worked other leads, but none strong enough to rule out the park.

At first, Tampa police officers searched with help from the Hillsborough Sheriff's Office, Hailey's family and friends and other volunteers. Meanwhile, a "Find Hailey Acierno" Facebook page garnered 2,500 members and Lisa's boss, Tampa attorney Steve Yerrid, offered a $25,000 reward for information leading to Hailey's return. Dozens of tearful supporters gather at the family's church to pray for her by candlelight. Clear Channel donated space on 12 digital billboards throughout the county.

By Thursday, Ward had asked the Pasco Sheriff's Office and Florida Fish and Wildlife Commission to join the effort. Searchers from the four agencies converged on the park with all-terrain vehicles, mountain bikes, horses, search dogs, even a drone. The whine of motors and scent of diesel fuel filled what is typically a quiet, idyllic spot for cyclists and runners, prompting county officials to close the park.

The searchers fanned out into grids, scanning the upland terrain and swampy terrain dominated by palmetto bushes, pine trees and oak trees. The thick brush often made for slow going, said Tampa police Lt. Michael Stout, who served as deputy incident commander for the effort.

"Literally, movement was at a crawl, day in and day out," Stout said. "We try to be slow and methodical because the last thing we wanted to do was leave with any doubts about the clarity of our search."

Shortly after the search resumed Friday morning, Tampa police bicyclists pedaled down a main off-road trail that runs south of the park's paved seven-mile loop to the Hillsborough River. Longtime mountain bikers in the area know it as the 1800 Trail.

It was an area that Hailey was familiar with, and one that searchers, including her father, had covered earlier, Ward said.

"You could walk that path a hundred times and never locate her," Ward said.

Hailey was wearing the clothes described in public notices seeking help in locating her — a yellow cap, black T-shirt and black jeans, with an M&Ms book bag. No note was immediately found with the body, police said.

Grief counselors were scheduled to visit Wharton High on Friday and Monday to offer help, a school district spokeswoman said.

"Certainly the outcome is not what we wanted it to be," said Stout, the police lieutenant. "But being able to give a family closure so that they're not spending day in and day out wondering means a lot to all of our officers that were out here."

Lisa Acierno expressed the family's gratitude in a Facebook post Friday afternoon.

"As much as we are mourning, I need to thank each of you for the indescribable support and prayers during the last 11 days," the post said. "We can only pray that Hailey found the peace that she longed for. Our lives will never be the same, but we truly feel the prayers and strength you all have provided. As I have said too many times, thank you is insufficient."

Contact Tony Marrero at tmarrero@tampabay.com or (813) 226-3374. Follow @tmarrerotimes.