TAMPA — It wasn't the red stains that looked like blood that made Kirby Mack think something was wrong with the car he borrowed from a friend.
It was the stench.
Mack, 38, was warned by friend James Monroe Sheets II not to open the trunk. But the odor was too overwhelming, according to a search warrant filed this week.
He pulled over. Inside the trunk, he found a body that Tampa police have identified as the car's owner, Henry Hilliard Shell III, 79, who had been reported missing Monday.
Mack's next move was "like something you would see in an episode of CSI," said Andrea Davis, a police spokeswoman.
Mack called authorities immediately Tuesday, told them about the body in the trunk, then drove the 2006 gold Mercury Grand Marquis to Tampa police District III headquarters at 3808 N 22nd St. He honked when he arrived.
A detective noted the body in the trunk and red stains "that appeared to be blood" on the driver's seat, passenger's seat and door handles of both passenger-side doors, the warrant said.
Shell's death was being called unexplained, pending toxicology results from the Hillsborough County Medical Examiner.
Sheets, 35, was named by police as a suspect in the suspicious death. He has not been charged in connection with it, but he was arrested Wednesday on charges of grand theft motor vehicle, possession of the controlled substance Xanax and possession of drug paraphernalia.
Judge Walter Heinrich revoked his bail, jail records show, and Sheets was being held in the Hillsborough County Jail as investigators and doctors piece together what happened in the finals days of Shell's life.
Police said Shell was last seen alive Saturday at his insurance business, Shell Realty and Insurance, at 1309 N Florida Ave. in Tampa. He was with Sheets at the time, police said.
Investigators were working to identify the pair's relationship, but said Shell was known to reach out to those less fortunate.
"He would help homeless people and give them odd jobs at his business and his home," said police spokeswoman Laura McElroy. She said it's unclear if that's what happened here.
The two men left the business in Shell's car between 6:20 and 11 p.m. Saturday, heading to Wesley Chapel, police said.
Later, a co-worker who hadn't seen Shell for several days notified authorities, and Shell was listed as a missing person. The medical examiner used dental records to identify his body.
Friends say Shell was a widower and a loner. His wife, Joann Hixon Shell, daughter of former Tampa Mayor Curtis Hixon, died in 2002.
While Shell was running his realty and insurance business, Sheets was bouncing in and out of state prison, records show.
He served three stints of less than one year each since 2006 for petty theft, possession of a controlled substance, trafficking in stolen property and giving false information to a pawnbroker.
He was last released May 13 from the Apalachee Correctional Institution in Jackson County. Sheets served 10 months of a 14-month sentence for battery on a law enforcement officer and resisting arrest with violence.
Mack has his own history with the law. He has had six stints in prison on drug charges and was most recently released in September 2010, records show.
His family rushed to the police headquarters Tuesday night, thinking Mack would turn out to be the body in the trunk. Several said they saw him driving the car that day.
For now, police consider Mack a witness to a bizarre scene and await the medical examiner to see if the death was a crime.
Times staff writer Jessica Vander Velde and news researcher John Martin contributed to this report.