Two suspects are in custody after six family members, including a 16-year-old mom and her baby, were gunned down in a targeted and likely gang-related "massacre," according to the sheriff.

Both the 16-year-old and her baby were shot in the back of the head during the Jan. 16 mass shooting in the farming community of Goshen, according to Tulare County Sheriff Mike Boudreaux. The other slain victims were ages 19, 49 and 52, as well as a 72-year-old grandmother, who was sleeping in her bed, Boudreaux said.

"This family was targeted by cold-blooded killers," Boudreaux said at a news conference Friday.

The suspects and two members of the victims' family were in rival gangs, but the specific motive is not exactly clear, Boudreaux said.

Two suspects were taken into custody early Friday morning when authorities executed three search warrants as a part of "Operation Nightmare," Boudreaux said.

One was taken into custody without incident, but the second suspect "engaged in a gun battle" with ATF agents, the sheriff said.

The suspect was shot and is undergoing surgery, Boudreaux said. He's in stable condition and expected to survive, the sheriff said.

The suspects had been under 24/7 surveillance since they were identified on Jan. 23, the sheriff said.

"The public was not at risk," the sheriff said. "We didn't have enough evidence ... to make the arrest."

"Once we did have the DNA information, we jumped," he said.

This is a developing story. Please check back for updates.