HOUSTON – A kidnapping victim was shot to death Thursday during an FBI investigation at a northeast Houston home.

Investigators said FBI agents were conducting an operation at a home in the 7300 block of Elbert Street when the victim, 47-year-old Ulises Valladares, was shot and killed.

WATCH: Conroe police provide updates on kidnapping victim shot by FBI

Sources said Valladares was taken from a Conroe home in the 1700 block of Tyler Lane Wednesday morning.

Authorities said two men forced their way into the home around 8 a.m. Valladares and his 12-year-son were inside at the time. When Valladares answered the door, the men pushed their way in with guns, according to investigators.

READ: Kidnapping victim shot to death: Timeline of events

The men demanded money, bound Valladares and the child, and began searching the house for valuables. They kicked in the door to a bedroom where Valladares' brother lived, according to court records.

During their search for valuables, the child told police that he heard the men say that his uncle, who was not home during the break-in, owed them $8,000.

The men took Valladares from the house, left the child, and told him not to contact police or they would kill his father. The child was able to free himself and contact a neighbor to get help.

After a neighbor called the boy's uncle at work, he came home to speak with police. During the meeting, the uncle received a phone call around noon from an unknown person who was speaking Spanish and said he was a part of "El Cartel Del Golfo," a Mexican drug cartel, court records said. The caller demanded $20,000 for Valladares' safe return, according to police. When the uncle told the man he did not have the money, the man told the uncle to "figure it out" and to call back when he had it, according to court documents. The man also told the uncle that the house was being watched and they would kill his brother if they discovered that police were involved, court records said.

The uncle denied owing money to anyone.

The uncle later told investigators that he recently lent a relative money for house repairs and the relative repaid him with a car that he registered in his name.

Conroe police then contacted the FBI.

With help from the FBI, authorities were able to track the phone to a location near the relative's house.

They then tracked the phone to a Best Western on Bay Area Boulevard, where two men, Jimmy Tony Sanchez, 38, and Nicholas Chase Cunningham, 42, were detained. They are charged with aggravated kidnapping and aggravated robbery. Investigators said they may be charged with capital murder.

Further investigation revealed that Cunningham is married to the uncle's relative, according to court documents.

Valladares was not found at the hotel, but Cunningham told investigators that he was being kept at his girlfriend's house in the 7300 block of Elbert Street in Trinity Gardens in northeast Houston, according to court documents.

Investigators and the FBI went to the house where FBI agents made entry into the home where Valladares was being held.

Court records indicate that authorities found Valladares' with his hands bound tape.

According to sources, FBI agents accidentally shot Valladares. He was taken to LBJ Hospital, where he was pronounced dead.

Cunningham's girlfriend, 35-year-old Sophia Perez Heath, was questioned by investigators.

During the interview, she told investigators that Cunningham and Sanchez brought Valladares to her home Wednesday night. She said that when Valladares arrived, his hands were bound and there was something over his head, according to court records.

Heath told investigators that Cunningham told her that he needed to leave Valladares at her house and asked her to watch him.

She is being charged with aggravated kidnapping.

Houston FBI Public Affairs Officer Christina Garza said during a news conference on Thursday that several people were inside the northeast Houston home, including two children, at the time of the shooting. No one else was injured.

When KPRC 2 reporter Cathy Hernandez asked if the agents knew children were in the home, Garza said, "That's why we're here."

Further details of the shooting and the FBI investigation have not yet been released because the operation is ongoing, Garza said.

Cunningham, Heath and Sanchez appeared in court Friday. Cunningham and Sanchez were denied bond. A judge set heath's bond at $1 million. She was ordered to wear an ankle bracelet if she makes bond.

Neighbors react

Monique McKnight, a neighbor in Trinity Gardens, said she was awakened by the raid.

"It sounded like an explosion and that was about 3 or 4 o’clock this morning," she said.

Another neighbor, who didn't want to be identified, said, "We just heard gunshots. It was like four, pop, pop, pops.”

McKnight said the people living in the home had recently moved in.

“The kids and stuff that lived over there and I would tell them I would see them roaming around,” she said.

McKnight said she believes her neighbors are a family-- a father, mother and two school-aged children. She said the little girl attended school, but the boy did not.

"When the little girl would catch the bus, he would still be there, so he wasn't at school,” McKnight said.

FBI responds

The FBI agent involved in the shooting was placed on administrative leave pending the outcome of an internal investigation.

The FBI released a statement that read:

"FBI was conducting an operation at a home in the 7300 block of Elbert Street in Northeast Houston. During the course of the operation, an individual was fatally injured. The FBI's Evidence Response Team is on scene. As with any agent-involved shooting, the Shooting Incident Review Team will investigate the matter."

In another statement, the FBI said:

"A Shooting Incident Review Team (SIRT) has arrived in Houston, as is standard in all agent-involved shootings. The SIRT is comprised of experienced FBI Special Agents who conduct a thorough, factual, and objective investigation of the events. At the conclusion of its investigation, SIRT provides reports to the Department of Justice and the local police department and District Attorney’s Office investigating the incident.

"The FBI takes very seriously any shooting incidents involving our agents and as such have an effective, time-tested process for addressing them. In the interest of protecting the investigation's integrity, we cannot comment regarding investigative details."