The bullet lodged among the bones of his right hand sends pain up his arm, and doctors fear removing it now would do more damage.

Amit Adhikari can only wonder why a man he never met put it there. Police say he was the first victim in a three-day rampage this week by a gunman who seemed to be targeting motorists at random in Garland, Mesquite, Richardson and Plano.

Late Tuesday, Garland police arrested the man they say is responsible, Thai-An Huu Nguyen. The 22-year-old's family says he studies nursing, but he's also a felon with violence in his past.

In most cases, the shooter missed. But a second man was shot in the torso, and two children narrowly escaped injury. Though police have a suspect, a motive remains elusive.

"We talked with him through the night," said Garland police spokesman Joe Harn, "and we still don't have a clue why he was doing this stuff."

Mr. Nguyen was booked into Garland's jail and faces two counts of aggravated assault with a deadly weapon, two counts of endangering a child and one count of deadly conduct. Police say further charges are expected.

Mr. Adhikari, 27, was stopped at a red light in Garland with his girlfriend and her 4-month-old daughter Sunday afternoon when they heard gunshots. Then the car's windows shattered around them.

"Go, go, go!" his girlfriend screamed as broken glass fell over the baby.

They never even saw who was shooting at them.

"I thought I saw a dark-colored car – that's it," Mr. Adhikari said.

Two days later, police say, the sixth and final shooting in the spree occurred at an Asian restaurant in Garland. The restaurant, in the 4500 block of West Walnut Street, was less than a block away from one of the first attacks. So on Tuesday, officers swarmed the area in case he struck again.

About 9 p.m., a Honda Prelude with an oversized muffler pulled into the parking lot of the busy restaurant. The gunman climbed out, took a few steps toward the restaurant and fired two rounds into the wall just below a row of windows.

"He walks back to his car and drives away at a normal pace," Officer Harn said. The bullets did not penetrate the wall, and no one was injured.

About 90 minutes later, less than a mile away, an officer pulled over a car that matched the description. Mr. Nguyen was inside, police say, along with a pistol.

At Mr. Nguyen's home in Garland on Wednesday, his mother leaned back on the couch and stared at the ceiling. An Nguyen spoke of his son's arrest with amazement.

"Last night, what happened, I can't believe it," said his father, who speaks limited English.

Other family members said they didn't know of anything that had been bothering Mr. Nguyen recently

"He looked normal," said a younger brother, Tai Nguyen. "Just came home, took a rest and did his homework."

Members of the family, which emigrated from Vietnam in 2000, said Mr. Nguyen graduated from a Garland high school, worked at a plant assembling cable and studied nursing. After his arrest, he told police he attended Richland College, though officials at the Dallas community college could not immediately confirm that.

But Garland police have run into him before. In October 2006, he was arrested after a woman reported she'd been robbed at gunpoint by a man who fired several shots in the air and fled in a Honda Prelude.

Mr. Nguyen first told investigators he'd gotten into a fight with the woman. Then he said she had tried to rob him. "Nguyen continued to change his story," the arrest report says.

Meanwhile, officers began questioning him about a hit-and-run crash involving a Honda Prelude several months before, in which a 17-year-boy was left with severe head trauma.

The boy and two witnesses said they were in the street playing basketball when the car passed them several times. Finally, it accelerated and swerved toward them, hitting the boy.

Questioned about the crash by officers, Mr. Nguyen said he'd been in the area to buy heroin. He said the crash was accidental. Then he said someone else was driving.

He pleaded guilty to a misdemeanor assault charge in the reported robbery and to a felony charge of failing to render aid in the crash. He received six years' probation in all. He also has a charge from 2002 of carrying a weapon in a prohibited place.

Extensive criminal histories aren't typical among spree shooters, said Larry Hoover, director of the Police Research Center at Sam Houston State University in Huntsville.

"They're not gang-bangers," Dr. Hoover said. "It tends to be middle-class young males. It's almost close to a random lashing out."

But shooting sprees happen so rarely that it's difficult to develop a profile of the typical offender, said Dr. Phillip Lyons, a Sam Houston criminal justice professor with a doctorate in clinical forensic psychology.

"For many people, it seems to be more about inspiring fear in others than actually trying to harm them," Dr. Lyons said.

A spate of shootings this year on Southern California freeways left three people dead. And in Virginia, authorities arrested two teenagers in March after random shootings along an interstate. The attacks stirred memories of the Washington, D.C.-area sniper shootings six years ago that killed 10.

In the second shooting Sunday night attributed to Mr. Nguyen, 37-year-old Jose Mendoza was shot while waiting at a red light with his 9-year-old son. The boy was not injured, and authorities say his father will recover.

Before that night ended, a third shooting occurred in Mesquite. Then another motorist was targeted in Richardson on Monday afternoon, and a fifth Tuesday on the Bush Turnpike in Plano.

After six shootings, it seems remarkable that more people were not hurt. Officer Harn was asked whether police think Mr. Nguyen may have missed some targets intentionally.

"Any time anybody points a gun in somebody's direction and pulls the trigger," he said, "we have to take it that they're trying to shoot that person."

Doctors expect to take the bullet out of Mr. Adhikari's hand in two weeks.

Staff writers Tanya Eiserer and Scott Goldstein contributed to this report.