As detectives investigated the death over the weekend, a family member of Mr. Dunn’s alerted them to the video, which the teenagers had begun sharing with friends.
“As much as we tried, there wasn’t any law in the state of Florida that they violated,” said Yvonne Martinez, a spokeswoman for the Cocoa Police Department.
The police asked the office of Phil Archer, the state attorney for Brevard and Seminole counties, to review the footage. But the prosecutor’s office said it did not contain the evidence needed for a criminal prosecution.
In the statement, the prosecutor’s office said it was nonetheless “deeply saddened and shocked” by how Mr. Dunn died and the failure of the teenagers to help him in any way.
The low-quality, 2.5-minute cellphone video, was provided to The Times by Mr. Archer’s office and earlier obtained by Florida Today. It shows a man flailing in the middle of a body of water as the teenagers describe his struggle and laugh at him from the shore of the pond.
One of the teenagers, using an expletive, calls Mr. Dunn a junkie. Someone tells him not to expect any assistance: “Ain’t nobody going to help you, you dumb bitch. You shouldn’t have got in there,” he says.
About a minute into the video, the man appears to let out a whimper before submerging, fully, underwater.
“He just died!” a voice can be heard saying, as the others laugh.
Later, one of the teenagers appears to suggest that they call the police, only to be rejected by another.
The police identified and met with all five, who ranged in age from 14 to 18, Ms. Martinez said. None appeared to show much emotion.
“What I saw was not remorseful,” she said.
A Facebook user named Simone Scott, who identified herself online as Mr. Dunn’s sister, expressed frustration with the investigation and said “something should be done” in a video live-streamed on the social network on Thursday. A funeral service will be held a week from Saturday, Ms. Scott said on Facebook. She did not respond to a request for an interview.
“If they can sit there and watch somebody die in front of their eyes, imagine what they’re going to do when they get older?” she said about the teenagers.
She also said she wondered how Mr. Dunn, who she said was disabled and walked with a cane, ended up in the middle of the pond. She also expressed frustration with the investigation.
Surveillance footage obtained on Thursday from a neighbor showed that Mr. Dunn entered the pond on his own and did not appear to be coerced or forced to go in, Ms. Martinez said.