Border Patrol Tactical Units (BORTAC) are carrying M4 rifles with silencers, which are often used by the US military's special operators on secret missions, and holographic sights.
Read more about BORTAC here.
Source: Washington Post
The M4s have PEQ-15 infrared sights that are used in tandem with night vision-goggles.
Source: Washington Post
BORTAC agents are also wearing masks, noise-cancelling headsets, the US Army's latest Operational Camouflage Pattern uniforms, and are even carrying extra rifle magazines.
Source: Washington Post, Business Insider
Others are in helicopters, sitting shoulder to shoulder as if preparing for a tactical insertion, as the Washington Post noted.
Source: Washington Post