Five masked gunmen invaded a U.S. Virgin Islands hospital before dawn Wednesday and killed a patient who was recovering from gunshot wounds, a police spokeswoman said.

The men stormed into the hospital through a back door, tied up a guard and shot Shadrach Frett in his room on the third floor, spokeswoman Melody Rames said.

Only employees were being allowed into the Governor Juan Luis Hospital on the island of St. Croix as police and FBI agents investigated the crime scene, Rames said.

Frett, 28, was hospitalized on May 12. He was later arrested on charges of unauthorized possession of a firearm after police determined he was injured in a gunfight.

St. Croix is the largest of three islands in this U.S. Caribbean territory.