Updated Jan. 30: Revised throughout to include additional details.

A federal agent shot a kidnapping victim dead during a predawn raid at a northeast Houston home last week after the man grabbed his gun, authorities said.

Houston police CHief Art Acevedo said the FBI agent who shot Ulises Valladares, 47, around 3:45 a.m. Thursday didn't know that it was the victim who had grabbed his rifle.

"A well intentioned effort to rescue a man who had been kidnapped ended in a tragic outcome," he said.

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Valladares had been kidnapped the day before in Conroe, about 40 miles north of Houston, police said.

Two gunmen burst into a home, restrained Valladares and his 12-year-old son and demanded $8,000, Conroe police Sgt. Jeff Smith said. They took Valladares with them when they left, along with video-game systems and a sword, and told the boy not to call the authorities.

The boy managed to break loose after they left and went to a neighbor, who called police.

Police were speaking to the boy and his uncle — who also lived at the home — when the uncle got a ransom call from a man who claimed to have connections to the Gulf cartel.

Conroe police brought the FBI into the case at that point, and authorities tracked the call to a Houston motel. Federal agents detained three people at the hotel, then traced Villadares' phone to a house in northeast Houston.

Acevedo said that one of the FBI agents was using his M4 rifle to break a window into the home when someone started to pull at the weapon. Fearful for his safety, and that of the other agents at the scene, the agent fired two shots.

One bullet struck Valladares, who died at a hospital a short time later.

Several other people, including two children, were at the home at the time of the shooting, but no one else was injured.

The agent who killed Villadares has been placed on routine administrative leave, FBI spokeswoman Christina Garza said.

From left: Nicholas Chase Cunningham, Sophia Perez Heath, Jimmy Tony Sanchez Jr. (Montgomery County Sheriff's Office)

Nicholas Chase Cunningham, 42, and Jimmy Tony Sanchez Jr., 38, who were arrested at the hotel, face charges of aggravated kidnapping and aggravated robbery. Sophia Perez Heath, 35, who was at the house, faces a charge of aggravated kidnapping.

All three were being held Tuesday at the Montgomery County jail. Cunningham and Sanchez were being held without bail; Heath's bail is set at $1 million.

Acevedo said the FBI agents went into the operation with "the best of intentions.

"Everyone involved, their heart breaks," he said.

A lawyer representing Valladares' family, however, said that the incident involved "a roadmap of mistakes."

"We're not saying the guy went there with malice in heart so that he could kill a duct-taped hostage," Douglas York said. "But once they got there, they failed to protect the very person they were designed to do. And when you're holding a deadly weapon, I think you owe a duty to the hostage not to kill him."

Perrye Turner, special agent in charge of the FBI's Houston office, said the agency couldn't provide more details because the investigation is ongoing, adding that the FBI "takes very seriously any shooting incident."

Neighbor Monique McKnight told the Chronicle that gunfire woke her up. "It sounded like an explosion," she said.

McKnight said agents asked her about the children who lived at the home.

"I have no idea what would be going on in that house," she told KHOU. "A lot of times they didn't have utilities. The lights weren't on, so I don't know how they were living."

Smith told the Chronicle it was unlikely the kidnappers actually were linked to a drug cartel.

"This was not a random cartel thing," he said. "It appears somebody connected to the family was involved."

The Associated Press contributed to this report.