SAN FRANCISCO (KRON) -- Luigi Mangione was reported missing by his mother to the San Francisco Police Department less than one month before he allegedly assassinated a health insurance executive in New York City, according to the New York Police Department's chief of patrol. Mangione, 26, was arrested in Altoona, Pa., on Monday. The police said they believe that Mangione was the masked gunman who calmly pulled out a gun in Manhattan and assassinated Brian Thompson, the chief executive of UnitedHealthcare, before he fled the scene on foot. At his first court appearance Tuesday in Pennsylvania, the suspected killer struggled with officers as he arrived. “This is completely out of touch and an insult to the intelligence of the American people,” Mangione said as he was led into court. Luigi Mangione is led into the Blair County Courthouse for an extradition hearing December 10, 2024 in Hollidaysburg, Pennsylvania. (Photo by Jeff Swensen/ Getty Images) Investigators are probing the past year of Mangione's life searching for clues about what led up to Thompson's chilling death. The New York Times reported, "Mangione was in regular contact with friends and family until about six months ago when he suddenly and inexplicably stopped communicating with them. He had been suffering from a painful back injury, friends said, and then went dark." Mangione was born and raised in Maryland, has ties to the San Francisco Bay Area and his last known address is in Honolulu. His X profile page features photos of Mangione hiking beautiful trails in Hawaii and an X-ray showing screws in the lower spine. Thompson led the largest medical insurance company in the U.S. (Image via Luigi Mangione / Facebook) His mother was apparently so concerned about her son that she reported him missing in San Francisco on November 18, according to NYPD Chief of Patrol John Chell. From wealth and success to murder suspect, the life of Luigi Mangione took a hard turn A LinkedIn profile matching Mangione shows he most recently worked for a California tech company, TrueCar, in 2023. The company told KRON4 that he left his job in 2023. The San Francisco Chronicle reported that his mother filed a police report last month stating she believed he was still working for TrueCar in an office in San Francisco. No one had heard from him since July, she wrote. The San Francisco Standard was first to report on the SFPD's missing person report. The SFPD's report was confirmed by KRON4's New York sister station PIX11. On Tuesday, San Francisco Police Chief Bill Scott said his police department has been in communication with the New York City Police Department for the Mangione case, but he declined to talk about the report. Friends of Mangione told the Times that he suffered from severe back pain and left Hawaii in the summer of 2023 to get spinal surgery. Luigi Mangione is led into the Blair County Courthouse for an extradition hearing December 10, 2024 in Hollidaysburg, Pennsylvania. (Photo by Jeff Swensen/ Getty Images) Mangione was motivated by anger over "parasitic" health insurance companies and a disdain with corporate greed, according to a law enforcement bulletin. He wrote a manifesto decrying the U.S. health care industry as the most expensive healthcare system in the world. Mangione served as a counselor at Stanford University in Palo Alto, where he taught high school students in a pre-college program. His stint at Stanford happened in the summer of 2019 before his senior year at the University of Pennsylvania, an Ivy League university. He was honored as valedictorian for his high school class in 2016. Valedictorian Luigi Mangione gives a farewell speech to the Class of 2016 during commencement at Gilman School. (Nicole Munchel/The Baltimore Sun/Tribune News Service via Getty Images) Thompson, 50, was ambushed and killed last Wednesday as he walked alone on a sidewalk to a New York City hotel. Manhattan prosecutors charged Mangione with five counts, including murder. At a hearing in Pennsylvania Tuesday, defense lawyer Thomas Dickey said his client will not waive extradition and wants a hearing on the issue. Mangione was denied bail. The Associated Press contributed to this report.