Former Green Bay Packers linebacker Brady Poppinga is suing a Southern California hospital and several of its doctors -- claiming they contributed to his teenage son's tragic death last year. The ex-NFLer filed the suit in Los Angeles this week ... alleging multiple physicians at Providence Cedars-Sinai Tarzana Medical Center did not properly care for Julius Poppinga after the family had admitted the 17-year-old into the facility's ICU. In the suit, Brady and his wife, Brooke, say they brought in their boy on Aug. 27, 2023 with chest pains and breathing issues ... but despite 'round-the-clock attention from docs, he didn't get better. On Aug. 29, the Poppingas said in their lawsuit Julius was in and out of consciousness while fighting to breathe ... but at one point, he woke up and was "tearful and afraid" as he yelled to Brooke he thought "he was going to die." Waiting for your permission to load the Instagram Media. Brady and Brooke allege a doctor on the scene "negligently and wrongfully concluded" Julius was having a panic attack -- and prescribed him some medication. A short time later, they say Julius passed away. An autopsy, the suit states, determined Julius died of a pulmonary embolism. The Poppingas are suing for wrongful death due to medical negligence and more ... and are asking for unspecified damages. The two have actually spoken publicly about Julius' passing multiple times -- including back in June when Brooke described her late son as a "very compassionate" and "joyful human being."