Puerto Rico's justice secretary said Tuesday he has opened a criminal investigation against two prison guards who were escorting eight inmates who drowned, screaming for help, while shackled in a van covered in floodwaters.

Secretary Guillermo Somoza said authorities are reviewing pictures and videos that bystanders took at the scene to determine whether prosecutors should file charges of negligent or aggravated homicide.

Ten inmates were being driven back to prison after court hearings in the northern coastal city of Arecibo when the guards apparently took a shortcut to avoid flooded streets, Corrections Secretary Jesus Gonzalez Cruz said. A rush of water toppled the van.

Hector Serrano, who lives nearby, said he ran to the van as he saw it disappear underwater and joined another man in rescuing two inmates and the two guards by cutting a hole in the vehicle's roof. He said the guards refused to turn over the keys so they could rescue the remaining trapped prisoners.

"They were nervous," Serrano told reporters late Monday. "The guards did not want to let them out ... supposedly because they would run away."

Those inside were screaming, Serrano said. "They wanted to be saved ... They were desperate."
Somoza and Gonzalez said that Serrano and the fellow rescuer are being questioned, as well as the guards and several bystanders.

"There are a lot of versions," Gonzalez said. "If there was negligence, we want to identify the person responsible."

Gonzalez said one witness told police that he saw a guard try to open the van only to drop the keys in the water.

The inmates who died faced charges ranging from robbery to drug possession. Some had been arrested as recently as last week, Gonzalez said.

Maritza Lopez, the mother of one of the inmates who died, told reporters on Tuesday that she believes no one wanted to save her son.

"He was not an animal," she said.

Gonzalez said the law required the inmates to be shackled during the trip, but he questioned why the guards would drive through the flooded area.

He said the two guards will continue to work for the department as the investigation continues