The women were last heard from last week, and police visited the home twice — on Friday and Sunday — before finally entering through a broken back door and finding the house of horrors before dawn on Monday, North Las Vegas police Sgt. Chrissie Coon said.
"Multiple conversations we had with family and friends led us to put two and two together," Coon said.
Sorrells declined to speak with investigators following his arrest, Coon said. He was expected to be appointed a public defender at his next court appearance.
The police report said he showed no reaction when he was told he was under arrest in the deaths of his mother and sister.
Police believe he killed the two women before beginning to dismember his sister's corpse in the bathtub.
The mother's body was found wrapped so tightly in layers of clear plastic and blue painter's tape that police who entered the modest two-story stucco home described it as a mummy.
Officers also found black vinyl gloves at the foot of the stairs, trash bags, an empty bottle of bleach and patches of ripped-out carpet.
A handprint was found on a bathtub wall, and flesh on the tile floor, the police report said. A trash can was in the middle of the living room; a green wheelbarrow next to the fireplace.
One officer noted what appeared to be blood spray on couch cushions.
The chain saw was found disassembled on the kitchen counter, along with knives, screwdrivers and a drain plunger. Human blood was found on the chain saw blade.
Police said home improvement store video showed Darius Sorrells buying the machine Friday morning.
The Clark County coroner hasn't said how the women died.
Coon said they last had contact with family members and friends last Wednesday or Thursday. She said police were informed Friday that the women were missing and hadn't been seen at work.
Sorrells is the only suspect in the slayings, Coon said.
A motive remained unclear.