Question: Please briefly summarize this news article:

Feds Depict Deliberate Plot

PHOENIX—Federal prosecutors are assembling a case against suspected killer Jared Lee Loughner that portrays him as a man with psychological problems who was nonetheless competent enough to plot an assassination.

An undated photo released by the Pima County Sheriff's Office showing shooting suspect Jared Loughner.

Devlin Barrett reports on how federal investigators are working to make the case against accused shooter Jared Loughner in this weekend's massacre in Tucson. Plus, former House Majority Leader Tom Delay is sentenced to three years in prison.

Mr. Loughner appeared Monday in federal court—his head shaved, shackled at the waist and dressed in a beige jail jumpsuit—to hear the government's charges of murder and attempted murder against him.

Federal prosecutors will try to show that Mr. Loughner planned the Saturday attack that killed six people, gravely wounded Rep. Gabrielle Giffords (D., Ariz) and injured 13 others.

During the hearing, Magistrate Judge Lawrence O. Anderson asked Mr. Loughner whether he understood the charges, which could carry the death penalty. "Yes, I understand," he replied in a loud voice.

Mr. Loughner was assigned two federal public defenders, including Judy Clarke, who had represented Theodore Kaczynski, the so-called Unabomber, as well as Sept. 11 conspirator Zacarias Moussaoui. She stood beside Mr. Loughner (pronounced LOFF-ner) at the hearing, frequently resting her hand on his shoulder.

Investigators are still trying to piece together the events leading to Saturday's shooting. Mr. Loughner tried that morning to buy bullets at a Wal-Mart store but was turned away, and then purchased some at another Wal-Mart, say people familiar with the matter, who relayed the preliminary findings of law-enforcement officials.

Wal-Mart Stores Inc. said Mr. Loughner wasn't turned away from the first store but left before completing his purchase. "We stand ready to provide any information or video surveillance footage we may have to investigators," the company said in a statement.

Investigators are reviewing surveillance footage that allegedly shows Mr. Loughner in line Saturday to speak with Ms. Giffords in front of a Tucson supermarket, according to people familiar with the matter. He is seen standing behind U.S. District Court Judge John Roll, who was fatally shot moments later, these people said.

Interviews with friends, as well as online comments attributed to Mr. Loughner, suggest the 22-year-old high school dropout had struggled with mental-health issues.

Witnesses and bystanders waited inside a police barrier in the parking lot of the Safeway grocery store where Rep. Gabrielle Giffords (D., Ariz.) and others were shot Saturday.

Officials say Mr. Loughner had psychological problems but plotted his attack in a deliberate and orderly manner—buying a Glock 9mm semiautomatic pistol in November and bullets the morning of the shooting. He wrote notes that suggested a grudge against Ms. Giffords over a perceived slight during a 2007 public event.

Mr. Loughner's parents told investigators they didn't realize the severity of their son's mental problems, say people familiar with the matter. Campus police had been notified of his disruptive behavior during classes at a community college. He was expelled in October.

Mr. Loughner has a petty criminal record, but investigators have found no evidence he was ever treated for mental-health problems.

In October 2008, Mr. Loughner was idling at a stoplight in a green 1969 Chevy Nova lent to him by his parents when he leaned out of the window to scrawl graffiti on a street sign, according to a police report.

After his arrest, Mr. Loughner helpfully drew the symbol he had inked on the sign in the police officer's notebook: a design that looked vaguely like a combination of the letters C and X. Mr. Loughner told the arresting officer it meant "Christian," and he confessed to other acts of graffiti vandalism, the report said.

Mr. Loughner paid restitution and attended a diversion program as punishment, a court administrator said.

About a year later, Mr. Loughner applied to be a volunteer dog-walker at a local animal shelter. He went through several hours of training and worked for several weeks in early 2010. But he was asked to leave when he refused to obey orders to keep dogs away from a contaminated area. "He was not listening," said Kim Janes, the center's manager.

Federal authorities have charged Mr. Loughner with two counts of murder, two counts of attempted murder and a count of attempting to assassinate a member of Congress. More charges are expected, officials said.

The shooting highlights longstanding worries by federal officials of so-called lone-wolf attacks by individuals unconnected with any group.

The FBI in 2009 created a new counterterrorism initiative seeking to focus attention on such attacks. FBI Director Robert Mueller mentioned concerns about lone attackers Sunday, citing the Internet as a source of hate speech. "That absolutely presents a challenge for us, particularly when it results in what would be lone wolves or lone offenders undertaking attacks," he said.

Prominent political shootings involving members of Congress.

The FBI's concerns are illustrated by such high-profile attacks as the 1995 Oklahoma City bombing, the 1996 Olympic bombing in Atlanta, and the series of bombings carried out over nearly two decades by Mr. Kaczynski, who lived in a remote cabin in Montana.

Don Borelli, a former counterterrorism official with the FBI, said investigators worry about lone wolf suspects because they are so hard to catch before they strike.

"In situations where you have a guy just hatching a plot in his mind and putting his rantings on the Internet, and he has the ability to get a weapon legally, that's a huge challenge for law enforcement,'' said Mr. Borelli, who now works at the Soufan Group, a global security consultancy firm.

Write to Evan Perez at evan.perez@wsj.com, Devlin Barrett at devlin.barrett@wsj.com and Peter Sanders at peter.sanders@wsj.com

Summary:
Answer: Federal prosecutors are assembling a case against suspected killer Jared Lee Loughner that portrays him as a man with psychological problems who was nonetheless competent enough to plot an assassination.