OKLAHOMA CITY - Home video shows cooing baby Amario laughing and smiling.
It was recorded a few weeks ago, before he was murdered.
The tragedy for the family doesn't end there.
Also living there, 40-year-old Daniel Green, who investigators say is being held on first degree murder charges.
Blood stained footsteps are imprinted feet away from where children play.
"We heard the girl who came home to everything, we could hear her screaming," neighbor Sabrina White said. "We saw the ambulance come and then there where cops' cars that came up and down the road."
Homicide detectives are working to learn what happened leading up to the killings.
While many neighbors are shocked, some said they aren't completely surprised.
Some told News Channel 4 Green seemed peculiar when he paced up and down the street.
"I knew Danny, I talked to him all the time when I'm out walking my dog," Neighbor Titus Story said. "He seems like he's a little off."
His Facebook page is haunting to some.
Neighbors say he was cordial but very unusual.
"When he talked to you, it's like he's talking through you with pretty much everything that he said," Story told us.
When the crime tape was gone a loved one stop by to pick up belongings.
She couldn't bear to speak with us but we did talk with Rebecca's boyfriend, Amario's father, Mario Dominguez, by phone.
"There's no way I can rationalize what happened," he said. "I believe I'm in shock right now, I just don't know how to feel I feel lost."
Dominguez lived in the home about three years.
He just moved out two weeks ago and that was the last time he held his baby boy.
"He was full of life, he was just learning how to crawl he would stand up on his hands and feet and rock back and forth," Dominguez said.
The 16-year-old victim, Katherine, was scheduled to start school on Monday.
Mid-Del Schools released this statement: "We extend our heartfelt sympathies to the family during this tragic time."
Her mother, Rebecca, worked at Sonic for 15 years.
The company sends us this statement: "We send our heartfelt condolences to the family and friends. Counseling will be offered to all crew members who are deeply saddened by the loss of our colleague."
As for why this happened....so far police aren't releasing the motive.