State police are investigating a Texas couple with a hoard of high-powered weapons — including an AR-15 with a grenade launcher and bump stock — after Tewksbury police raised suspicions they were staking out the March For Our Lives last weekend.

Francho Bradley, 59, and Adrianne Jennings, 40, both of Frisco, Texas, are being held without bail pending a dangerousness hearing Friday after they were arraigned for breaking numerous firearms laws — and are facing the nation’s first charges for possession of bump stocks.

The pair had driven up from Texas and rented a motel room in Tewksbury for two weeks when Bradley called police on March 24 — the day of the march — saying the video feed he had set up in his room had been disrupted and he was worried someone had broken into his room, according to police reports.

When police arrived at the room, they reported finding an arsenal — in addition to the AR-15 coupled with a grenade launcher, weapons strewn about the room included an AK-47, two other semiautomatic rifles, a shotgun, two pistols and three smoke grenades classified as “infernal devices” under state law, along with tactical vests and hundreds of rounds of ammunition.

Bradley arrived at the motel after police and told law enforcement officials he had a Texas permit to carry a handgun — which is not recognized by Massachusetts. He reportedly told police he was “in this area working for a government agency that is dealing with a virus,” but would not say what that agency was.

But Tewksbury police Detective Patrick Connor thought the couple may have been in the area for another reason. Police said they found multiple parking tickets issued to Bradley by the city of Cambridge dated several days apart — two at the exact same location in Kendall Square and one near that spot.

“Based on his frequent trips to Cambridge from Tewksbury and arsenal of weapons, my suspicions grew that he may be surveilling an area,” Connor wrote in the report, adding, “it should also be noted that I knew there was a major demonstration ‘March For Our Lives’ in Boston that day.”

State police spokesman David Procopio said the FBI and Bureau of Alcohol Tobacco, Firearms and Explosives are investigating the pair along with state police and the Middlesex District attorney, but so far had not found any information that they were targeting or “scoping out” the march.

“We’ve interviewed (Bradley) and he’s made certain statements to us. We’re still investigating his purpose in going to Cambridge,” Procopio said. “So far we have not determined anything to establish a nexus between him and the march, and nothing to suggest a wider group or conspiracy.”

Bradley and Jennings are facing 45 charges overall, including multiple counts of possession of a large capacity firearm and possession of a machine gun (bump stock), authorities said.

In February, Massachusetts became the first state in the country to ban bump stocks in the wake of last year’s Las Vegas massacre. Officials said Bradley and Jennings are believed to be the first suspects arrested for violation of the ban.