James Brady, who has died aged 73, was the principal victim of John Hinckley's attempt to kill President Ronald Reagan. The bullet that lodged in the White House press secretary's brain on 30 March 1981 inflicted catastrophic neurological damage from which he never fully recovered.

However, it may have saved thousands of his countrymen's lives. Though Brady's injury left him severely disabled, the ease with which a disturbed young man could acquire a gun transformed him and his wife, Sarah, into tireless campaigners for more effective controls on America's sale of firearms. In 1993, in the face of enormous opposition, they were rewarded with the enactment of what became known as the Brady Law, requiring arms buyers to undergo mandatory computerised checks into their background.

Though the gun lobby had whittled down many of the act's original provisions, research into its five-year impact showed that it had reversed a rising trend. Between 1994 and 1998, some 10,000 fewer Americans were gunned down than in the five years before the Brady Law came into force. It was a melancholy triumph for a man who had achieved a lifelong ambition when he became Reagan's official spokesman after the 1980 election.

He had been obsessed with politics from his earliest years in his home town of Centralia, Illinois, where he was born the only child of Harold and Dorothy. Even as a student he had wangled a job working in Washington for one most influential senators to have come from the state, the Republican minority leader Everett Dirksen. It gave him a fascinating glimpse into the realities of the legislative world. When Brady graduated from the University of Illinois in communications and political science in 1962, that experience determined the pattern of his subsequent career.

After a brief stint as a lecturer at Southern Illinois University he was recruited as spokesman for the Illinois State Medical Society (1966-68), a highly political job in an environment where medical bills are the greatest single cause of personal bankruptcy. After lobbying for the doctors he moved into the world of corporate public relations, in part because he had also become active in the organisation of successive Republican election campaigns at state and national level.

In 1973, with the Watergate crisis gripping the nation, Brady moved to Washington to take up a series of political appointments, first with the department of housing, from 1975 with the budget office, and the following year at the Pentagon. The advent of the Jimmy Carter administration put paid to this job, as it did for those of thousands of other Republican special assistants, and he joined the staff of a Republican senator. Four years later, with the Iranian hostage crisis blighting the Carter presidency, Republican hopefuls started jockeying for the party's 1980 nomination. Brady's amiable manner on Capitol Hill and his shrewd political reflexes had caught the attention of one of these presidential contenders, John Connally. The former governor of Texas recruited him to cope with the media during the imminent round of gruelling primary elections. In what later became an eerie coincidence, Connally had himself been seriously wounded by an assassin's bullet – he was in the car with John Kennedy when the president was killed in Dallas in 1963.

Brady did a splendid job for Connally until it became evident that the Reagan juggernaut was rolling over all his opponents. Though Connally dropped out of the race, the sterling performance of his spokesman had clearly attracted attention. When Reagan roared into the White House by a margin of 489 electoral votes out of 538, he immediately asked Brady to take over as the presidential press secretary.

It was as well that the president-elect had as sharp a sense of humour as his new spokesman. One memorable moment had been Reagan's observation that "approximately 80% of our air pollution stems from hydrocarbons released by vegetation". After the election, reporters were flying over Northern California in the White House plane when an apparently hysterical Brady began pointing at the redwoods and gasping: "Killer trees, killer trees." We were sworn to secrecy but someone inevitably blabbed.

A couple of months after taking office, the president's address to an AFL-CIO trade union conference appeared to be another routine chore. Brady had made the short trip from the White House only in case there was any awkwardness with the delegates. In fact, all went smoothly until he led the presidential group out of the Hilton hotel. The first of Hinckley's six bullets, an explosive .22 Devastator, hit the left side of his head and he fell unconscious. A bullet lodged in Reagan's lung after ricocheting off his limousine.

It was amazing that Brady made any recovery at all. After months of intense treatment he was able to retrieve most of his mental powers, but used a wheelchair for the rest of his life. His designation as White House press secretary was maintained throughout the Reagan presidency, though his colleagues actually filled the role. In February 2000, as a tribute to his astonishing resilience and his continuing campaigns to extend gun controls and to improve the treatment of disabled people, President Bill Clinton formally named the White House briefing room in his honour.

He married Sarah (nee Kemp), his second wife, in 1973. She and their son, Scott, survive him, as does his daughter, Melissa, from his first marriage.

• James Scott Brady, public relations practitioner, born 29 August 1940; died 4 August 2014

• Brady Campaign to Prevent Gun Violence