WASHINGTON—The shooting at a gay nightclub in Orlando early on Sunday has reignited congressional debate over terrorism and the country’s gun laws, as lawmakers grappled with responding to one of the deadliest shootings in U.S. history.

Congressional leaders, including House Speaker Paul Ryan (R., Wis.) and members of the House and Senate intelligence committees, were briefed on the attack Sunday. (See an interactive map and timeline showing how the Orlando attacks unfolded.)

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