PHOENIX (AP) — A Tucson man faces federal charges after allegedly shooting at U.S. Border Patrol agents and trying to ram their cars with his SUV in the most serious among a spate of migrant smuggling attempts near the Arizona-Mexico border over the long Christmas weekend.

The U.S. Attorney's Office for the District of Arizona says that 21-year-old Roberto Ramirez of Tucson was charged Wednesday with offenses including assault on a federal officer, use of a firearm in a violent crime, and high-speed flight from a border patrol checkpoint. During his initial court appearance, it was ordered that Ramirez remain in custody.

U.S. Border Patrol Agent Daniel Hernandez, public affairs officer with his agency's Tucson sector, said Thursday that smuggling attempts are not uncommon in the region, but "we did see a higher level of activity over the holiday weekend." Authorities discovered at least three other human smuggling attempts in southern Arizona over the holiday period, but no other case involved violence. In all instances, U.S. citizens drove the vehicles and migrants hid in car trunks or traveled as passengers.

The federal complaint against Ramirez alleges that he arrived Sunday at a Border Patrol checkpoint on Interstate 19 near the tiny community of Amado, about 30 miles (50 kilometers) north of the border city of Nogales, Arizona. Agents suspicious about the two passengers in the Ford Escape directed Ramirez to secondary inspection, but he sped away on the northbound interstate with several border patrol vehicles in pursuit.

During the Christmas eve chase, police allege Ramirez fired several gunshots at agents and tried to strike their vehicles with his SUV before rolling the vehicle over and crashing. One of his two Mexican passengers was ejected and seriously hurt.

Ramirez and his two passengers were taken to a hospital for treatment of their injuries and released. The passengers are being charged with immigration offenses. The federal charges against Ramirez carry a maximum penalty of 20 years of imprisonment and a $250,000 fine, according to the Arizona division of the U.S. Attorney's Office.

There were 93 assaults on Border Patrol agents in the Tucson Sector during the federal government's 2017 fiscal year, with 786 assaults nationwide, the U.S. Attorney's Office said in a release about the case. Border Patrol Agent Hernandez noted that a vehicle can be as deadly as a firearm.

At the same immigration checkpoint near Amado on Saturday, Border Patrol agents arrested a 20-year-old woman from the Phoenix suburb of Tempe after discovering two men and a woman in the trunk of her Chevy Malibu.

Agents searching the vehicle also found a loaded firearm that belonged to the driver.

Border Patrol agents additionally reported two human smuggling attempts over the long holiday weekend farther to the east.

On Dec. 22, agents at the State Route 90 Immigration checkpoint arrested a 20-year-old Phoenix woman driving a Chevy Cobalt along with two male Mexican migrants — one traveling as a passenger in her car and the other in the trunk.

A canine team patrolling State Route 80 stopped a Buick Lacrosse sedan driven northbound by a 61-year-old Arizona man, and the dog detected a 23-year-old male migrant in the trunk. Authorities detained the migrant and the driver, a U.S. citizen.