Houston police identify the victims as 29-year-old Donyavia Lagway, 35-year-old Gregory Carhee and their daughter, 6-year-old Harmony Carhee.
Their 10-year-old daughter was shot in the arm. Her 1-year-old brother was not injured.
An 8-year-old brother was spending the night with family. The shooting happened inside their apartment at 12101 Fondren Wednesday night.
"I still can't believe it," Manda Lagway told ABC13.
The 10-year-old called Lagway on FaceTime for help after the shooting. "She's like, 'Granny, my mom got shot. My dad got shot' and I'm like, 'What happened?'"
The news was jarring.
READ ORIGINAL STORY: 'Brave' 10-year-old played dead, called grandma after family killed
The family called police and by the time Lagway and others got to the apartment, it was blocked off with crime scene tape. The surviving girl told police the killer knocked first.
He had a mask on and grabbed her baby brother by the hair and threw him. He then shot the victims in the head.
She said she played dead and when the killer left, she got her brother and locked the door.
"I just want everybody to know my baby, she's a hero. My baby is a hero," said Lagway.
Friends and family dropped off balloons and candles on Thursday, still stunned by what happened.
"Someone's sick. It's sickening," said Gloria Johnson, Donyavia's friend.
Detectives canvassed the apartment complex and recovered surveillance video in their search for the person who shot the family. Police say the suspect is in his 20s though they have not released a motive.
"That's a monster. You don't do that," said Johnson.
Anyone with information is urged to call Crime Stoppers or the Houston Police Homicide Division. A reward is being offered for information that leads to a charge or an arrest.
For updates on this case, follow ABC13 reporter Jessica Willey on Facebook, Twitter and Instagram.