Houston, Texas - A man armed with an assault rifle opened fire at a Border Patrol facility in Texas on Monday before being shot dead, officials said.

The Department of Homeland Security (DHS) said two police officers and a Border Patrol employee were injured, including one who was shot in the knee and hospitalized.

The shooting took place at the entrance of a Border Patrol annex in McAllen, Texas, a DHS spokesperson said, and was being investigated by the FBI.

"Both Border Patrol agents and local police helped neutralize the shooter," the spokesperson added.

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A motive for the shooting was not immediately known.

Local media quoted McAllen police chief Victor Rodriguez as identifying the slain gunman as Ryan Louis Mosqueda (27).

Mosqueda fired dozens of rounds from an assault rifle before being shot dead, according to Rodriguez.

Other weapons were found in his vehicle.

The incident comes amid aggressive deportation efforts carried out by President Donald Trump's administration, which have raised tensions and sparked waves of protests across the country.