A Texas dad called cops on his mentally ill son — warning that he was trying to buy guns to carry out a mass shooting, according to authorities.

The terrified dad dialed 911 to say that his disturbed son was off his meds and hellbent on getting weapons for a rampage, the Fort Worth Police Department said Tuesday.

The unidentified 27-year-old had withdrawn about $700 and was trying to buy guns on the street after getting flagged at gun shops as having failed background checks, according to NBCDFW.

“He wanted to kill many people,” officer Buddy Calzada told the station.

“He wanted to do something that was very similar that took place in the Midland-Odessa area and he basically wanted to mimic that,” he said, referring to Seth Ator, who killed seven in a 10-mile rampage earlier this month.

Officer Landon Rollins, one of the cops who finally cornered the man in downtown Fort Worth last Tuesday, said the suspect was confused and thought he had died and was in hell.

“When asked why he was trying to obtain a weapon, he was just very flat and blunt — to kill people,” Rollins told the Fort Worth Star-Telegram. “He said, just, ‘I want to kill people.’ He reiterated this many times. He was … not living in reality.”

Rollins praised the unidentified dad for putting others’ safety first and reporting his own son.

“He was extraordinarily worried and he feared a mass casualty incident,” Rollins told NBCDFW. “That takes so much courage to be able to do that on your own family and to reach out to law enforcement for that.”

The suspect was diagnosed with several mental health issues and is at a local clinic receiving treatment, according to the reports. Decisions on possible charges are pending, police said.

“Our utmost concern is making sure he receives the care he needs,” Calzada told the Star-Telegram. “Once an evaluation about his care has been determined, a decision will be made from there.”