FRISCO -- Montana Brown was only 15 years old when he died in December in Frisco.
His last breath was the first clue that a lethal new drug was spreading among North Texas teens.
"Everyone loved Montana. The spontaneous vigil, we had had 300-400 kids at it," said his dad, Eric Brown.
He said his son was a straight-A student and athlete.
Brown's other two sons overdosed at the same time.
"My oldest son was in ICU for three days,” he said. “My middle son had no comprehension [of] what happened."
The drug was a synthetic form of LSD commonly called "N-bomb" or "Smiles." It is the same one believed to have sent three McKinney children to hospitals on the same day in early April.
"One was wandering in one part of McKinney, and the other was wandering in another part of McKinney, naked," Brown said.
A close relative of the third teen phoned Eric Brown, and agreed to talk to us if we protected her identity. She told us by phone that she has spoken with other students and parents who tell her at least 10 children took the drug. Police only confirmed three.
She said the other kids had less-severe reactions. She said the child, in her case, is 14 years old and the other two are eighth graders.
"They're being told it's some kind of happy thing,” she said. “That it's really harmless and that it makes them really happy. And it's a lie."
Synthetic LSD has been blamed for at least 20 deaths in the last two years, including two in Houston and one in Louisiana.
"But it's probably a much larger number,” Eric Brown said, “because hospitals don't detect it. And coroners don't know to look for it."
He said his son was screened for 56 different substances before identifying the chemical that sent him into convulsions.
The North Texas Poison Center reports an increase in calls about it; 25 through April 5.
"It increases the heart so much, the heart just gives out," said the center’s Orlando Llerena.
Experts say it's actually a hallucinogenic amphetamine.
"Extremely dangerous,” Llerena said. “Just one drop causing people to go to the emergency room."
The DEA said the chemical usually comes from China. It's applied to paper squares or even candy. According to families affected, it's easy for kids to get.
"I just want parents to take this very, very serious,” said the relative of the teen. “Very serious."
In her case, the child spent three days in the hospital.
The 24-hour number for the North Texas Poison Center is 800-222-1222.