The 17-year-old was taken into custody at North Shore High School yesterday after one of his friends warned authorities he had a gun and might be thinking of hurting himself.
Two deputies found him in the common area, patted him down and handcuffed his arms behind his back with his arms restrained in the back of the police cruiser, the student managed to shoot himself in the head.
"I know he was searched. He may have had it hidden really well. All I know is that when he was in the squad car, he grabbed a gun and shot himself," Galena Park ISD spokesperson Jonathan Frey said.
Ray Hunt with the Houston Police Officers Union says it is possible to miss a handgun during a search.
"It was just that person wanted to harm themselves. When you do that, you secure the person and go get additional information. It could be that's what happened and he just missed it," said Hunt.
And that is likely what happened in this case, the Harris County Precinct 3 Constable's Office said on Thursday.
Precinct 3 Capt. Jon Moore said preliminary results from an internal affairs investigation indicate a full search wasn't done because the 17-year-old student had not been arrested and was only detained so authorities could get him help.
Friends of the teen say he posted about wanting to commit suicide on social media.
A letter was sent home with students, notifying parents of the incident. There will be grief counselors on campus today, available to talk to students.
"There are some kids who do need to go and just talk things out," Frey said. "I think it's even important to know that kids have that available. Sometimes students don't know they need help until something like this happens."
Dr. Ann Saunders is a child psychiatrist with the UT Harris County Psychiatric Center. She says the common warning signs are a change in sleep habits, more irritability and anger, a withdrawal from family and falling grades. What helps is an observant parent who's attentive to their child.
She said, "If you just, as a rule, are inquiring about what your kid is doing and encourage them to give an idea of how they're feeling or doing and without being judgmental, they're much more likely to do that."
Some teens are offering support to each other via a Facebook group called the Sunshine Project. It encourages teens who are suffering depression to get help.
The teen is reportedly still in critical condition at Ben Taub Hospital after undergoing surgery.
The Harris County Sheriff's Office is investigating the incident. Moore says so far, it does not appear deputies violated any policies or procedures.
The Associated Press contributed to this report