A Wells Fargo armored truck guard was shot and critically wounded yesterday when he was robbed outside an Arlington bank. Three men, all Salvadorans, were arrested last night near Perryville, Md., and charged in the holdup, officials said.

Arlington police said the wounded guard, Charles O. Scruggs, 48, of N. French Street, Alexandria, was shot once in the chest at point-blank range as he was delivering an undisclosed sum of money to the United Savings Bank branch at 3141 Lee Hwy., in the Lyon Village Shopping Center. Scruggs was in critical condition last night after surgery at Arlington Hospital.

Another Wells Fargo guard, who had remained in the armored truck, was unharmed, police said.

Two hours later, three men from Northern Virginia were arrested after Maryland State Police stopped their car for a routine traffic check as the men were driving north on Rte. I-95 north of the Susquehanna River, the FBI said last night.

The FBI and Maryland police said Carlos Antonio Campos, 22, of 1676 N. 21st St., Arlington; Jesus Basilio Hernandez, 23, of 527 Four Mile Run Rd., Alexandria, and Jose Santa Urrutia, 24, of Philadelphia face federal charges of bank robbery and interstate transportation of stolen property.

State police said $40,000 in new $10 and $20 bills was found. They said they believe that to be the total amount taken in the robbery.

Pfc. Gary Berge, who stopped the men's car, said last night that he pulled over their 1979 Mazda sports car shortly before 2:30 p.m. because of an apparent license plate violation.

State police said Berge, a nine-year veteran, was working at the John F. Kennedy Memorial Highway toll booth just north of the Susquehanna River as part of a drug interdiction team and noticed that the Mazda had no front license plate and no visible rear plate.

Berge summoned a patrol car and he and another officer pursued the auto and pulled it over about three miles north of of the toll booth, police said. They said that as Berge approached the car, a large stick, a knife and what appeared to be ammunition were visible.

Believing that the car might be involved in transportation of drugs, Berge ordered the men out of the car. It was then that a quantity of .45-caliber ammunition, a loaded .45-caliber automatic pistol and a white bag containing new $10 and $20 bills were found in the car, police said.

The men were taken to the Perryville state police barracks, officials said, while the federal Drug Enforcement Administration was notified. When the sack of money was described to DEA officials, they told state police of the armored truck robbery.

The three men offered no resistance, he said. The car in which the suspects were riding is owned by one of the men, police said.

Berge said the three men would be held overnight at the Cecil County Detention Center. Police said it was unclear how long they had been in this country.

The robbery and shooting occurred shortly before 12:30 p.m. when two men approached Scruggs as he was delivering a bag of money.

Police said a bullet entered Scruggs' upper left chest and exited through his back.

The gunman and his accomplice ran up a hill behind the bank onto the Rte. I-66 bicycle trail and fled eastward. The area was searched by a Fairfax County police helicopter, a U.S. Park Police dog, which became exhausted and had to be called off because of the scorching heat, and then by Arlington police dogs, police said.

"I was unloading my truck when I saw some suspicious guys," said James McNeely, a cigarette distributor. "The man from Wells Fargo . . . had the door open, like he was ready to put the bag in there. Then I heard 'pow!' The guard said, 'Hey' after the 'pow' and I saw him look down and begin to fall. He shut the truck door a little bit . . . . The other guard in the truck was yelling to get an ambulance."

"We were getting ready to go into the Peoples drugstore when we heard a shot that sounded like a firecracker," said Debora Kaufmann, who had stopped at the shopping center with her friend, Anne Hamilton.

"I turned around and looked, saw these two gentlemen with a gun pointed by one of them at the Wells Fargo truck . . . . I suddenly realized what was going on and said, 'My God, this is a robbery.' " Kaufmann said the gunman grabbed a white canvas bag from the wounded guard and ran to meet his partner, who was standing outside an adjacent florist shop.

The two women then ran into the drugstore to ask for an ambulance, they said.