Raegan Day and her friend, Dustin Hartline, never showed up at the home of relatives in Kenner where they were expected on Feb. 15, triggering concern among family and friends that mounted with a missed appointment in Baton Rouge.
Their anxiety turned to grief Monday when St. Tammany Parish detectives, acting on a tip, went to the East Pearl River Boat Launch and found the 20-year-old woman's dark blue Camaro in the East Pearl River.
The bodies of the missing pair were found inside.
On Tuesday, the Sheriff's Office had four suspects in custody, each booked on two counts of first-degree murder.
Jason Landry, 18, and Brittney "Beezy" Savell, 25, both of Slidell, were arrested with the help of the Waveland, Mississippi, Police Department and the U.S. Marshals Service.
Derrion Lemoine, 22, of Lacombe, and Steven "Stevie" Olivieri, 27, of Slidell, also were arrested, and additional arrests are possible, the Sheriff's Office said.
Autopsies were conducted Tuesday, but no statement on how the two victims died was issued.
Sheriff Randy Smith said he will hold a news conference to discuss the case Wednesday morning.
The deaths bring the number of homicides in St. Tammany Parish this year to three. Last week, 7-month-old Carter Nauck was killed, and his father, Corey Nauck, was booked on first-degree murder.
Sheriff's deputies and family members had searched for the pair for more than two weeks, initially concentrating their efforts on the Eagle Lake Boulevard off U.S. 11 between Slidell and Pearl River, according to WWL-TV. That's the last place the two were known to be, according to cellphone records.
The two lived at the same residence in Pearl River. Hartline was 28.
Court records from the 22nd Judicial District show that Olivieri's rap sheet goes back to 2008. He has pleaded guilty to bank fraud, possession of marijuana, aggravated assault and simple burglary, among other charges.
Lemoine also has a record in the 22nd Judicial District and has pleaded guilty to carnal knowledge of a juvenile, a misdemeanor, and felony counts of criminal damage and simple burglary dating back to 2014.
Savell pleaded guilty to a misdemeanor charge of simple battery in 2013.