Questions are being raised after a 54-year-old man involved in a child custody dispute was charged with murder in the shootings of his two children in Texas, one of them fatal.

Predrag Perisic, who was supposed to return the children to their mother in Montreal, had previously had been charged with interfering with child custody in Harris County, Texas.

Police said they were climbing to the second floor of his home north of Houston when they heard gunshots, according to a statement from the sheriff's office. Inside they found Perisic and his two wounded children.

The 10-year-old-boy named Deyan was pronounced dead at a nearby hospital.

His 12-year-old sister, Danyela, was airlifted to Memorial Hermann Hospital in Houston, where she was listed in stable condition Tuesday.

The children were reported missing in late October.

According to a child custody complaint filed last month, the man failed to return the children to his estranged wife as ordered by the Quebec Superior Court.

Pina Arcamone of the Missing Children's network said parents involved in custody battles can sometimes take extreme measures.

"Too often we hear parental abductions being trivialized, and a lot of people automatically assume they are safe," she said. "We can't afford to do that."

Family members say there were many episodes of verbal and physical violence between the mother and father.

The mother of the children, Vera Vucerakovich, chose to come back to Montreal with her kids after trying to reconcile and live with the father in Texas in the summer of 2009. They returned to the city last January.

It was at that time that the father in Texas applied to have his kids returned to him and have a custody hearing in Texas.

Perisic remains in San Jacinto County Jail in Coldspring, Texas, without bond under a murder charge. Jail officials had no information on whether he has an attorney.

Vucerakovich was en route to Texas on Tuesday.

Police in the Houston suburb of La Porte learned the children had not attended school since Oct. 25 and that Perisic had called the school the next day, saying they wouldn't be returning to class because they were returning to Canada, the Houston Chronicle reported.

Court records show Perisic and the children's mother, are Canadian citizens and he had filed for divorce earlier this year, the Chronicle reported.

- with files from The Associated Press