On May 26, 2021, a mass shooting occurred at a Santa Clara Valley Transportation Authority (VTA) rail yard in San Jose, California, United States.

[7] The VTA is a public transportation agency that operates bus and light rail services throughout Santa Clara County and employs about 2,000 workers.

[17] At 6:33 a.m. the San Jose Fire Department received a call to respond to the VTA facility, though the first caller did not mention anything about an active shooter incident, according to dispatch audio.

[19] A minute later, Santa Clara County authorities received 9-1-1 calls about shots being fired at the VTA facility.

[20] The shooting began in a conference room in Building B, on the western side of the yard, during a power crew meeting with the local Amalgamated Transit Union president, who was spared.

Two minutes later, the fire department responded to the home in South San Jose, about eight miles (13 kilometers) away from the VTA facility, and discovered hundreds of rounds of ammunition and a gas can there.

[14] Police received reports of explosive devices inside the building, prompting a bomb squad to investigate.

[6] Sheriff's deputies searched the gunman's house for three days, finding a total of 12 guns, 25,000 rounds of ammunition, and a dozen Molotov cocktails.

[15] Cassidy's ex-wife, who had been married to him for ten years before their divorce in 2005, described him as having anger issues and often being angry at his co-workers and at the VTA for what he believed to be its unfair work assignments.

[15] According to an initial review by the VTA, Cassidy had a pattern of insubordination and had gotten into verbal altercations with coworkers on at least four separate occasions.

[39][40][41] According to coworkers, Cassidy was angered over a change in policy that ended cash payouts for unused vacation days and, in April 2021, aired his grievances over the radio communication system for light rail operators.

[25] An August 2016 memo by the United States Department of Homeland Security (DHS) described how, after taking a trip to the Philippines, Cassidy was detained by officers with U.S. Customs and Border Protection (CBP) for a secondary inspection.

Santa Clara County district attorney Jeffrey F. Rosen said that, had his office been alerted about Cassidy's detainment, they would have had enough evidence to obtain a gun violence restraining order and seize his weapons.

[46] Mayor Sam Liccardo said it was a "horrific day" for the city and the VTA, and he expressed his condolences to the victims and their families.

[5] The day after the shooting, a vigil was held outside San Jose City Hall and attended by hundreds, including the victims' families and many VTA employees, who were dressed in their work attire.

[49] On June 22, the San Jose City Council made plans to introduce a resolution commemorating the victims' lives.

On August 2, a free bus bridge began serving portions of the Blue and Orange lines between Paseo de San Antonio and Milpitas stations.

[63][64] As of December 2021[update], the Santa Clara County Sheriff's Office and an outside law firm retained by the VTA are both conducting investigations into the shooting.

[69] On June 15, the San Jose City Council unanimously approved an ordinance requiring, among other things, retailers to record video and audio footage of gun sales, with the intention of preventing straw purchases of firearms.

[73] On September 30, 2022, District Judge Beth Labson Freeman issued a partial dismissal on NAGR's lawsuit against San Jose's gun control ordinance, which had been consolidated with a suit by the Howard Jarvis Taxpayers Association, with leave to amend in part and without leave to amend in part.

[7] Although Cassidy did not use an assault weapon, Attorney General Rob Bonta cited the San Jose shooting in a statement opposing the ruling.

Issues with information-sharing between agencies had been a problem in recent years and has sometimes involved high-profile incidents such as the storming of the U.S. Capitol and the Stoneman Douglas High School shooting.

[80] Liccardo met with Biden on July 12 to discuss strategies on combating gun violence in the U.S.[81] Following the shooting and rising anti-Asian sentiment in the United States, a petition was started, demanding officials to address concerns made by employees of the San Jose Public Library over their safety.