GAINESVILLE, Fla. -

Police in Gainesville are filing a murder charge against the 18-year-old suspect in a University of Florida student's disappearance, investigators announced Friday evening.

Pedro Bravo is accused of killing his childhood friend, 18-year-old Christian Aguilar. The teen's body hasn't been found. Aguilar disappeared Sept. 20.

"The body of Christian Aguilar has not yet been recovered. The Gainesville Police Department will continue its search efforts for Christian Aguilar and would still encourage citizens to volunteer to help us in that search," said Gainesville Police Officer Ben Tobias at a news conference Friday.

In a release, police ask for the public's help in searching for Aguilar.

"We would also encourage property owners, residential or business, who may have lime rock roads on their property, that were accessible to the general public, to search those properties for any suspicious areas of ground that appear to have been disturbed," the release states.

Police said Bravo was at Best Buy at 3 p.m. Sept. 20, as seen on surveillance video with Aguilar, his childhood friend. Aguilar hasn't been seen since. Investigators said they also know where Bravo was in Gainesville at 8 a.m. the next day, but they don't know where he was for the time in between.

When Bravo retained legal counsel, investigators said they reached out to his attorney, but they have not yet responded.

Investigators said earlier this week that Bravo bought a shovel and duct tape several days before Aguilar went missing.

Bravo is currently in the Alachua County jail on a charge of depriving a victim of medical care.