The maintenance worker who fatally shot nine co-workers at a San Jose light rail yard before killing himself Wednesday was under investigation at work because colleagues had complained about his racist remarks, law enforcement authorities told KNTV in San Jose. 

A number of the victims at the Santa Clara Valley Transportation Authority facility were people of color. 

There were no details of the exact nature of the remarks reportedly attributed to Samuel Cassidy, 57, who has been identified as the shooter in the massacre. Sources told the NBC TV station that Cassidy also boasted about the firearms and explosives he owned.

Cassidy came to work the day of the shooting with a duffel bag packed with three semi-automatic handguns and 32 high-capacity magazines, The Associated Press reported. He appeared to target his victims as he fired at least 39 rounds.

“It appears to us at this point that he said to one of the people there: ‘I’m not going to shoot you,’” Santa Clara County Sheriff Laurie Smith told AP on Friday. “And then he shot other people. So I imagine there was some kind of thought on who he wanted to shoot.”

Law enforcement and fire authorities responded to reports of a blaze at Cassidy’s home minutes after the shootings erupted. The fire was sparked by a timed explosive device. Investigators discovered suspected Molotov cocktails, cans of gasoline, 12 firearms and 22,000 rounds of various kinds of ammunition at the home, the Santa Clara Sheriff’s Office reported Friday.

“Based on current evidence obtained by Sheriff’s Office Detectives at the VTA yard and the suspect’s residence, it is clear that this was a planned event and the suspect was prepared to use his firearms to take as many lives as he possibly could had Sheriff’s Deputies not made entry to stop his rampage,” the sheriff’s office said in a statement.

Cassidy was able to obtain the weapons even though he was questioned in 2016 by Customs and Border Protection after he returned from a trip to the Philippines carrying books on terrorism and a diary about his hatred of his workplace, The Wall Street Journal reported. It was not clear if CBP ever forwarded that information to local law enforcement authorities.

Cassidy’s ex-wife, Cecelia Nelms, told AP that he struggled with his temper and talked about killing his co-workers more than decade ago.

Sheriff’s investigators portrayed Cassidy as a “highly disgruntled VTA employee for many years.” They haven’t yet determined a motive for the shootings.

Hundreds of people gathered Thursday night outside San Jose’s City Hall to honor and remember the victims, who ranged in age from 29 to 63.

“We’re here to share our pain, we’re here to share our love, to share our support for each other,” San Jose Mayor Sam Liccardo said after reading their names. “We’re here to express a singular message in our community: We will heal, and we will heal together.” 

One of the victims was Taptejdeep Singh, a member of the Sikh community, who spent his last moments warning his co-workers to stay in their offices and calling others coming into work to warn them about the shooter.

“Because of him, so many people were able to go home to their families,” said his brother, Karman Singh, in a statement. He had “a lion’s heart.”

Taptejdeep Singh, 36, leaves behind a wife, a 3-year-old son and a year-old daughter.