WASHINGTON — A pregnant teenager, her mother and 12-year-old brother were found murdered in a gruesome scene in Alabama, in what investigators believe was a premeditated and calculated killing.

Mobile County Sheriff Paul Burch told local TV station WALA that deputies found a mother and child stabbed and a pregnant teenager shot inside a Wilmer, Alabama, home on Monday. However, the teen’s 18-month-old child was inside the home uninjured.

Officials identified the victims as 46-year-old Lisa Fields, 17-year-old Keziah Luker and 12-year-old Thomas Cordelle Junior.

According to the sheriff, investigators believe multiple people entered the house and tied up the victims in separate rooms.

“They had a plan when they came in,” Burch said during a press conference Monday. “All of the victims had their hands bound behind them with zip ties or flex cuffs.”

Once the victims were subdued, officials said the perpetrators began killing them.

“The mother was stabbed, the 17-year-old was shot, and the 12-year-old’s throat was cut as was the mom,” Burch said. “It tells me that they had a plan coming in to bring zip ties or flex cuffs with them, so they had a plan.”

“The 12-year-old was almost decapitated. And so it was a brutal scene, and I hope and feel comfortable we’ll have this animal, or animals, off the street soon,” Burch described.

Investigators said there were no signs of forced entry. The sheriff said it’s clear the suspect, or suspects, were searching for something in the house.

The scene was discovered when the father of the unborn child, who was working offshore, became concerned when Keziah Luker stopped answering her phone.

Officials told WALA he sent a family member to check on the house. That family member found the bodies.

“They went in, saw part of the scene, collected the 18-month-old, and called 911,” Burch said.

Now, the victims’ loved ones are searching for answers.

“No matter what the circumstance was, I mean a child, two children, lost their life. A seventeen-year-old and a twelve-year-old over senselessness and a child that had a child in her stomach,” Luker’s father told WALA. “We lost everyone for nothing.”

Sheriff’s office investigators have not released any details about suspects, but told WALA there were some positive leads in the case.

CNN Newsource contributed to this report