Christian Aguilar chatted on his cellphone Thursday with a friend from Doral Academy Preparatory School in West Miami-Dade.

Though he was a freshman at the University of Florida in Gainesville and she was at the University of Central Florida in Orlando, they kept in contact.

Both planned to purchase Kanye West’s new CD, Cruel Summer, listen and compare notes.

That afternoon, Aguilar got the album and posted a picture of it online, using the Instagram photo-sharing service.

His friend, Alyssa D’Bazo, waited for his call.

It never came.

Later Thursday, Aguilar went missing. Now, dozens of friends, family and strangers from across the state have flooded the woods of Gainesville, searching for him. His father, Carlos Aguilar — who has waded through the brush, calling out his son’s name — pleaded for help on television.

Monday evening, police arrested another 18-year-old from Doral Academy — the last person to have seen Aguilar.

Pedro A. Bravo, 18, was not charged in Aguilar’s disappearance. He was charged with “depriving a victim of medical care,” a third-degree felony, according to Gainesville police.

Bravo was arrested, police said, because he said he fought with Aguilar Thursday night, then left him in a parking lot. The two had been friends in high school, but later had a falling out.

No one has seen or heard from Aguilar since.

Bravo has given police hazy details of the fight. He said he left Aguilar in the parking lot of Streit’s Motorsports, near the 4900 block of Northwest 13th Street. Officer Ben Tobias, a police spokesman, said investigators found nothing there.

“There’s no evidence of him where Pedro said he should be,” Tobias said.

At the time of his arrest, Bravo was being held under Florida’s Baker Act after making comments to police about wanting to kill himself. He was transferred to the Alachua County Jail after he was released from a psychiatric evaluation.

Bravo’s arrest surprised friends of Aguilar who had traveled to Gainesville to join his distraught family’s search.

“I can’t imagine him doing anything,” said D’Bazo, who searched Monday night with Nicole Montero, a Florida International University freshman.

D’Bazo described Aguilar as a lanky, awkward teen with a brilliant mind and an eye for design.

Though very smart, he wasn’t very confident.

“He never felt like he was good enough,” she said. “But he was pretty much better than most of us.”

Doral Academy Principal Douglas Rodriguez said Aguilar was popular at the school and graduated near the top of his class. Bravo graduated in the same class.

On Monday, the Doral faculty and staff mobilized after hearing Aguilar’s father make his plea on TV. As many as a dozen teachers, assistant principals and even the principal himself headed to Gainesville.

The school has collected about $2,000 to help the family while they remain in Gainesville.

“We want to do anything we can to find Christian. He’s part of our family,” Rodriguez said. “A lot of manpower is needed, and we want to help.”

D’Bazo described Bravo as funny, smart and a little short.

Montero also knew him in school. “I never thought anything weird,” she said.

While in high school, Aguilar took dual-enrollment classes at Miami Dade College, and was a few classes away from getting an associate’s degree in biology.

After his high school graduation, he enrolled at UF.

“Christian wanted to go to UF since forever,” D’Bazo said. He wanted to become a heart surgeon or an architect. A huge fan of the university, he plastered his bedroom walls with Gators posters and teased friends who preferred other schools.

Bravo had initially planned to attend Florida International University, but changed his mind and went to Santa Fe College, also in Gainesville.

Bravo’s ex-girlfriend, Erika Friman, whom he had dated for about two years while they attended Doral Academy, enrolled at Santa Fe as well.

Then, Friman and Aguilar started dating at the beginning of the semester.

Aguilar and Bravo stopped talking.

D’Bazo said Thursday night would have been the first time Aguilar and Bravo had met up since their falling out. Exactly what happened while they were together remains a mystery.

“I think that’s what kills me the most,” Montero said of Aguilar, “that he’s out there alone.”

Miami Herald Staff Writer Luisa Yanez contributed to this report.