[3] He survived the 2018 Stoneman Douglas High School shooting and subsequently advocated for gun rights, notably in opposition to his fellow survivors' March for Our Lives movement.

[6][7][8] He later petitioned President Donald Trump to award Peter Wang, a student who had helped several others escape before he was killed, the Presidential Medal of Freedom.

[5][16] In April 2018, Kashuv criticized CNN for being biased because one of their contributors, Joan Walsh, had liked a tweet by Fred Guttenberg, whose daughter died in the Stoneman Douglas High School shooting.

[19] The Miami Herald in July 2018 wrote that the conservative Second Amendment supporter Kashuv had "gained a national following as a counterweight to the March For Our Lives" movement.

[14] Associated Press in February 2019 described Kashuv as "the most prominent conservative voice among the students" who had survived the Stoneman Douglas High School shooting.

[20] Kashuv became director of high school outreach of the conservative[14] group Turning Point USA and gave speeches about gun rights, including at Princeton University.

[21] Kashuv invited Turning Point USA founder Charlie Kirk to address Marjory Stoneman Douglas High, but the school did not permit the activity.

[22] Kashuv helped to plan the organization's 2018 High School Leadership Summit for over 800 students, and was lauded by Fox News in July 2018 as "a role model for young conservatives across the country".

[14][18] He resigned from Turning Point in May 2019,[24] hours after former classmates threatened to make public screenshots of racist remarks Kashuv had made.

[6] Following the Stoneman Douglas High School shooting, Michael Gruen, a 19-year old "influencer marketer", noticed Kashuv's posts on Twitter and approached him offering to help him get his message out.

[32] Kashuv said he agrees with fellow student activists David Hogg, Cameron Kasky and Emma González that gun deaths and school shootings need to be stopped, "and that shouldn't be delegitimized, ever".

Kashuv's stated solutions to improve the situation differ from Hogg and Kasky's, but he has called for a debate with them to find "common middle ground".

[26][43] Screenshots of a Google Doc for a class study guide showed Kashuv writing the n-word multiple times, discussing "JEWISH SLAVES", and declaring that he would "fucking make a CSOG [sic] map of Douglas and practice" (in a supposed reference to the Counter-Strike: Global Offensive shooter game and Stoneman Douglas High School).

[46][47] In an interview with The New York Times, Kashuv said that the comments on the Google Doc were made late at night, and that he had "said a bunch of anti-Semitic stuff".

[6] On June 17, 2019, Kashuv stated that the comments were made "months before the shooting",[48] and also said that Harvard University had rescinded its offer of admission as a result of the remarks.