A Los Angeles man is suspected of stabbing his live-in girlfriend and her 2-year-old daughter in their home, killing the little girl and critically wounding her mother, who was five months pregnant, authorities said Tuesday.

The man was arrested following a tip from the suspect's father, police Captain Peter Whittingham said at a news conference.

"We really do appreciate a father's ability to recognize his duty in this case," he said.

Lataz Donald Gray, 22, could face charges including murder and attempted murder and was being held without bail, according to Officer Liliana Preciado. She didn't know if Gray has an attorney.

The woman's unborn child will survive and was not injured in the attack, Whittingham said. Investigators said Gray was not the 2-year-old girl's father. The stabbings followed an argument at the residence, police said.

Officers responding to a 911 call late Monday found both victims with multiple stab wounds on the floor of the home near downtown, Preciado said.

Gray was receiving medical treatment at a hospital for a cut to his hand Tuesday when he contacted his father and told him about the stabbing, Detective David Garrido told the Los Angeles Times.

The father persuaded his son to turn himself in and then contacted police, who arrested Gray at the hospital.

The toddler died at a hospital. Her 22-year-old mother remained hospitalized in critical but stable condition and was unable to talk to detectives.

There were no witnesses to the attack.