A man with an assault rifle opened fire on a border patrol building in McAllen, Texas, early on Monday and was shot dead by federal officers, the police said.

At about 6 a.m. local time, officers from the McAllen Police Department responded to the U.S. Customs and Border Protection’s McAllen Station after reports of a shooting, Police Chief Victor Rodriguez said.

No federal officers were injured in the shooting, but a local police officer was injured in the knee, either by a bullet or shrapnel, he said.

The authorities found other weapons in the man’s car, which was in a parking lot. The chief said there was spray paint writing on the vehicle that officers could not decipher.

A motive for the shooting, which was being investigated by the Federal Bureau of Investigation, was not immediately known. Chief Rodriguez said the man, who was not publicly identified, had been reported missing on Monday morning.

Flights were delayed at the nearby McAllen International Airport early on Monday, the airport said. The chief said the delays were caused because vehicular traffic was kept away.