THOUSAND OAKS, CALIFORNIA – Another mass shootout in the United States left another region stricken with grief, grief and questions over what could have motivated someone to shoot down a dozen people in a western bar. The massacre that killed 12 people – including an 18-year-old man who had just started university, a Marine and a sergeant who rushed to confront the gunman – also left behind uncertainty about the way a neighbor-shooter was concerned and that prompted a mental health check of the police was able to legally obtain the handgun used in the attack. The carnage of Thousand Oaks, a community of about 130,000 people near Los Angeles, was very much like recent shootings in churches, cinemas, schools, community centers and offices. Police said 28-year-old Ian David Long, a former sailor, opened fire on a security guard with a .45 caliber handgun, then went inside, filming the staff and then guests of Borderline Bar & Grill. he had gathered for his university evening. [The 12 lives lost in the California bar shooting] When Sergeant Ron Helus of the Ventura County Sheriff's Office went inside to confront him. The former officer was shot repeatedly and fatally. The officers then found Long in a bar office, dead from a seemingly self-inflicted gunshot wound. The investigators are still trying to figure out what could have motivated Long, looking for clues to his state of mind in search of personal, car and social media accounts. Sheriff Geoff Dean, of Ventura County, said it did not seem like Long was targeting particular people inside the bar. "Of course, he had something in his head that would make him do something like that," Dean told reporters. "So he obviously had problems." Dean, who had already announced his intention to retire at the end of Friday, said he was spending his last days at the office in reaction to the shooting: "It can not be worse." [Inside, it was ‘like hell.’ Another mass shooting in another public place claims 12 lives] Those who escaped the disaster – some of whom had also survived the massacre of 58 people at a country music festival in Las Vegas last year – described the gunman as methodical and silent. "It was a very stern face, with a straight, focused face," said David Anderson, 23, of Newbury Park, who experienced the Las Vegas shootout and the Thousand Oaks attack. "Did not say anything." People who had met him for a long time described him as being angry and troubled. Attempts to contact Long's mother and other relatives were unsuccessful. The neighbors of the house where Long lived with her mother, Colleen Long, recounted a tendency to annoying behavior that left some unsuspecting to hear that he had been named a shooter. Carol Richardson, who lives nearby, said a friend had gone home several times to "calm down" him, and his 19-year-old daughter, Morgan, said, "We have always knew that he had problems. the border has become a familiar sinister ritual across the country. The information on the shots gives way to the stories of several people struck or killed. Then stories of chaos, horror and heroism emerge from those who escaped. And, as was the case after the Parkland, Florida, attacks in Sutherland Springs, Texas, questions began to appear about red flags before the bloodshed and what officials law enforcement could or should have done. [Thousand Oaks gunman had ‘several contacts’ with police over the years] In at least one case, Long's problems attracted the attention of the police. Dean said the police met Long in April when they were called for trouble. Long was acting irrationally, so they set up a crisis response team to meet him, Dean said. They discussed the possibility that he "is suffering from PTSD," said Dean, noting Long's service in the Marines. (Long deployed in Afghanistan between 2010 and 2011 and having left the Marines as a corporal in March 2013). This team "met him, talked to him and acquitted him" and did not have the feeling of being able to detain him under a so-called 5150 Order, Dean told reporters. Under a 5150 order, a person considered "a danger to others or to herself" can be arrested for up to 72 hours – which would have prevented her from owning or possessing weapons fire. The police did not publish more information about the April meeting and about how Long had been eliminated, but the neighbors recalled hearing alarming noises and screaming from the house in the middle of the night. A relative recalled that his home had been cleaned up and that Dean had stated that the Glock gun used in the attack had apparently been bought legally, which also echoes the conclusions drawn in previous attacks. In 2013, most assailants, usually men or boys, carried legally obtained firearms, and the shooters had worried the people around them before the attacks. Officials were only able to verify that 25% of these perpetrators had diagnosed mental health problems. In Thousand Oaks and beyond, the shooting sparked vigils and new calls for new gun control measures. Schools were closed and a center of the city reserved for families in mourning. [The Las Vegas shooting survivors who went on to survive this latest massacre] Dean, the sheriff, had planned to attend his retirement party on Saturday, crowning eight years as county sheriff and 41 years in the department. He had just returned home Wednesday night after someone else's retirement party when he received an SMS on the set of the bar. He put on his uniform and headed for the Borderline for a sleepless night. On Thursday, he went to tell the families of the people killed at the border that their relatives were among the victims. His last day of work would be devoted to the response to the massacre, while the retirement party scheduled for Saturday was canceled. "It will not happen," said Dean while he was in the street near the border on Thursday afternoon. "I'll be here tomorrow and I do not know where I'll be on Saturday," said Berman from Washington. Katie Zezima in Thousand Oaks, California, and William Wan, Frances Stead Sellers, Alice Crites, Julie Tate and Jennifer Jenkins in Washington contributed to the writing of this report. .