Testimony continued Wednesday in the trial of a Miami man charged with killing University of Florida student Christian Aguilar.
Pedro Bravo faces several charges in the 2012 death of Aguilar, his one-time friend and former classmate at Doral Preparatory High School.
During Wednesday's half day of testimony, a former cellmate of Bravo said he described how he killed Aguilar and asked for his help in covering it up.
Michael Angelo, a convicted gang member turned jailhouse informant, testified that Bravo told him he watched 13 minutes tick off his car's clock while he strangled Aguilar to death.
Angelo says when Bravo arrived at the jail he cried often and spent his time staring at the ceiling. He said Bravo asked him for a pencil to write a suicide letter and for Angelo's shoelace so he could commit suicide.
Prosecutors say Bravo wrote the letter, which was found by a guard. In it Bravo said he was "a monster for hurting Chris the way I did."
Prosecutors say Bravo orchestrated a plan to kill Aguilar over an obsession with former girlfriend Erika Friman, who was dating Aguilar in Gainesville.
Bravo researched ways to kill and get away with it before drugging and strangling Aguilar in a WalMart parking lot, prosecutors said. Defense attorneys said the two had argued, but denied that Bravo killed Aguilar.
Aguilar was reported missing in September 2012, setting off a massive search. The 18-year-old's body was later discovered by hunters in a rural area of Levy County.
Police said they found blood in Bravo's SUV and found Aguilar's backpack hidden inside a suitcase in Bravo's closet. Bravo also bought a shovel and roll of duct tape days before the disappearance of Aguilar, a UF freshman, according to authorities.
Bravo faces seven charges, including homicide, kidnapping, poisoning, making a false report, obstructing a criminal investigation, destroying evidence and mishandling human remains.