FRESNO, Calif. -- Police are combing through video footage of a woman who recorded herself smoking methamphetamine before shooting her two young children, their father, a cousin and herself, seeking clues into a weekend tragedy that unfolded in California's Central Valley.

The apparent murder-suicide by Aide Mendez, 23, began Sunday morning when she argued with Eduardo Lopez, the father of her two children. Authorities say that at some point that morning, she used her iPad to record herself and her boyfriend's cousin taking drugs.

After neighbors called police to report trouble, officers arrived to find Lopez outside the apartment complex with knife and gunshot wounds, said Lt. Mark Salazar, a police homicide commander.

They heard a muffled shot from the first-floor apartment and discovered Mendez had killed herself, the cousin, 27-year-old Paul Medina, as well as her two children, 17-month-old Aliyah Echeverria and Isaiah Echeverria, 3.

Police told The Fresno Bee they found Mendez in the bathroom and the children in the apartment's bathtub, where they had been shot at least once. The boy had died at the scene, Salazar said. The girl died at a hospital.

"We do know that drugs played a key role, but we don't know to what extent," Salazar said. "She was seen prior to the shooting smoking methamphetamine. She recorded herself on an iPad showing her and Paul Medina smoking meth. We know the power of meth."

Salazar said the time stamp on the iPad video would have to be tested but preliminary information indicated it was recorded within a few hours of the murder. Police do not immediately anticipate releasing the footage.

"Her actions just seemed bizarre; her mannerism, the way she was moving her hands and her facial expressions," Salazar said, noting other drugs may have been involved but that it would take weeks before the toxicology reports were complete.

Lopez, 33, remained in critical condition late Monday at Community Regional Medical Center with stab wounds and a gunshot wound to the neck, said Mary Lisa Russell, a hospital spokeswoman.A 7-year-old neighbor girl who was in the apartment escaped unharmed.

Authorities said they had yet to piece together a motive, but that family members reported that Mendez had lost a baby several years ago, and was still grieving over the loss.

Police recovered 10 grams of meth, $8,000 in cash and three firearms in the apartment; two of them used.

"There's some things we just don't know because most of the people in that house are dead and the one person who is alive can't speak right now," Salazar said.

A neighbor, Jesus Gonzalez, told KFSN-TV, an ABC affiliate in Fresno, that he heard gunshots and pounding on his door. He found Lopez bleeding profusely.

"I opened the door and he fell in front of me, and I take him and I pull him inside," Gonzalez said. He said that before he could drag Lopez inside, Mendez tried to pull him back outside again.

Gonzalez said he shouted, "Hey, what happened, what happened?" and she ran off.

The family lived in the back of the gated apartment complex in southeast Fresno, which has neat lawns, trees and a children's playground.

Neighbors said there was no indication of violence between the couple before the shootings. "They would come out with the baby carriage, and the man was taking care of his children," neighbor Eric Gonzalez said.

Another neighbor said residents were struggling to comprehend what had happened.

"It just really gets you thinking about how a mother could just grab her kids and kill them," Lizeth Gonzalez, a mother of three children who lives in the complex. "I never thought it would happen here. Whatever she did, I hope God can somehow forgive her."