HOUSTON (KTRK) -- Houston police are investigating what appears to be a murder-suicide inside a home in southwest Houston.A 9-year-old girl found her mother and stepfather dead in the home at the 4900 block of N. Cancun. She immersed called 911, according to police."She is very cooperative. (A) very intelligent young lady. She was able to tell us exactly what happened (and) what she heard," detective Christopher Elder said.Infant triplets were also home at the time but none of the children were harmed.Neighbors heard gunshots around 9:20am but didn't report it to police.Neighbors said that the couple had been arguing for the past couple of months.The woman was in her late 20s and the father in his mid 30s.Romeo Edmund lives nearby and said he knew the family but didn't see any problems. He said this should be a reminder to everyone to look out for each other."We need to talk to one another more often," Edmund said. "People might be going through issues."The children are being placed in the care of relatives.