(CNN) -- Sarasota, Florida, prosecutors are planning to charge a 16-year-old boy accused of killing two British men as an adult.
"The facts support our seeking two counts of first degree murder," Assistant State Attorney Karen Fraivillig said late Monday.
Sarasota police arrested Shawn Tyson at 3 a.m. Sunday, 24 hours after they discovered the shooting victims, James M. Cooper, 25, and James Thomas Kouzaris, 24, both from England.
Police were alerted to the incident by a 911 caller who said "a person was lying on the ground covered in blood" at the scene, on a one-way residential street.
Sarasota Police Chief Mikel Hollaway said officials are trying to determine why the men were there.
"We have our suspicions, but at this time it would be unfair to state those," he said. "I believe they were there of their own volition."
Police are asking for people seen with Cooper and Kouzaris in surveillance pictures from Friday evening to contact police. In a statement released Tuesday, Marissa Moore of the Sarasota Police Department, said the people are not suspects. "We would like to contact these individuals so that we can learn more details about the victims' activities" and other people who may have been in contact with them, she said.
The neighborhood where the British men were found is a housing project in north Sarasota called Newtown, Hollaway said.
The teen suspect lives near the crime scene, a police report said, and he had been arrested previously this month on a charge of aggravated assault with a handgun.
Although the housing authority has worked to improve the complex, "it has its problems," Hollaway said. "This is an isolated incident."
The two men were believed to be friends who recently graduated from college and were in Sarasota to celebrate.
Prosecutors plan to convene a grand jury and seek an indictment in the case, expected sometime in May.