John Hummel, 34, had nothing to say on his way into the Tarrant County jail.
Deputies picked him up in San Diego, where he was arrested after he fled briefly to Mexico, police said.
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The part-time security guard allegedly stabbed his pregnant wife and allegedly struck his daughter and father-in-law with a baseball bat before setting fire to the family’s home, prosecutors said in court documents.
"I would have never guessed that he was capable of something like this,” said the father-in-law’s sister, Cylinda Bedford.
In court, family members came face-to-face with Hummel, but he avoided looking at them.
"It was chilling, bone-chilling,” Bedford said. “He still doesn't look like a guy who's capable of doing something like this, but obviously he is."
In a brief court proceeding, Tarrant County District Judge Ruben Gonzales advised Hummel of the charges against him and appointed an attorney to represent him.
The family initially thought the fire was caused by bad wiring but now has no doubt he committed the crime, Bedford said. The family is left with one question, she said.
"Why?” she said in an interview outside the courtroom. “You could get a divorce. You can separate. You can move to another state. There's no reason for any of what he's done."
Family members said Hummel often played the fantasy game Dungeons and Dragons.
On his MySpace page, he used the nickname "John Fire Dragon.”
In his last entry, 11 days before the slayings, he wrote, "Too much going on in my mind to think str8t."
He didn't explain.
"I believe in the justice system,” Bedford said. “He'll get what's coming to him."