A gunman who killed nine of his co-workers at a rail yard in San Jose, California, had stockpiled weapons and ammunition at his home, including 12 guns and 22,000 rounds of ammunition, authorities said on Friday. Investigators found the cache of weapons at the home of Samuel James Cassidy, the Santa Clara county sheriff’s office said in a news release. They also turned up multiple cans of gasoline and suspected molotov cocktails. Authorities have said that Cassidy set his house on fire using a timer or slow-burn device to coincide with his attack. The guns he used to open fire on his co-workers appear to be legal, officials said. They have not said how he obtained them. Investigators were still trying to determine what might have set off Cassidy, who for years apparently held a grudge against his workplace. Cassidy was reportedly due to attend a disciplinary hearing on the day of the attack. NBC Bay Area reported on Thursday night that his scheduled disciplinary hearing followed an investigation by his employer over complaints he made racist remarks to co-workers. Wednesday’s attack was marked by horror and heroism, leaving nine men dead ranging in age from 29 to 63. Taptejdeep Singh, the 36-year-old father of a three-year-old son and a one-year-old daughter, was on an early shift as a light rail operator when the shooting began. He called another transit employee to warn him, saying he needed to get out or hide. “From what I’ve heard, he spent the last moments of his life making sure that others – in the building and elsewhere – would be able to stay safe,” co-worker Sukhvir Singh, who is not related to Taptejdeep Singh, said in a statement. Kirk Bertolet, 64, was just starting his shift when shots rang out, then he heard the screams. He and his co-workers threw a table in front of their door, and Bertolet called the control center. Then there was silence. Cautiously, Bertolet left the barricaded office, hoping he could offer first aid. He couldn’t. He saw some of his co-workers take their last breaths. Bertolet, a signal maintenance worker who worked in a separate unit from Cassidy, said he is convinced Cassidy targeted his victims, because he didn’t hurt some people he encountered. “He was pissed off at certain people. He was angry, and he took his vengeance out on very specific people. He shot people. He let others live,” he said. Cassidy fired 39 bullets. Camera footage showed him calmly walking from one building to another with his duffel bag to complete the slaughter, authorities said. “It appears to us at this point that he said to one of the people there: ‘I’m not going to shoot you,”’ said Laurie Smith, the Santa Clara county sheriff. “And then he shot other people. So I imagine there was some kind of thought on who he wanted to shoot.” Cassidy’s ex-wife said he had talked about killing people at work more than a decade ago. Cecilia Nelms told the Associated Press that he used to come home from work resentful and angry over what he perceived as unfair assignments. He also spoke of hating his workplace when customs officers detained him after a 2016 trip to the Philippines, a Biden administration official told the AP. A Department of Homeland Security memo said Cassidy also had notes on how he hated the Valley Transportation Authority, according to the official. It doesn’t say why he was stopped by customs officers. It said he had books about “terrorism and fear and manifestos” but when he was asked whether he had issues with people at work, he said no. The memo notes that Cassidy had a “minor criminal history,” citing a 1983 arrest in San Jose and charges of “misdemeanor obstruction/resisting a peace officer.” San Jose police said in a statement through Mayor Sam Liccardo’s office that they sought an FBI history on Cassidy and found no record of federal arrests or convictions. “Whatever this detention at the border was, it did not result in an arrest that showed up on his FBI criminal history, and it was not reported to SJPD,” the statement said. Neighbors, acquaintances and an ex-girlfriend described him as a loner, unfriendly and prone at times to fits of anger. Documents show he had worked at the transit authority since at least 2012. Bertolet described Cassidy as anoutsider. “He was never in the group. He was never accepted by anybody there. He was always that guy that was never partaking in anything that the people were doing,” Bertolet said.