Arkansas--An Arkansas doctor, accused of seeking revenge on the state medical board who repeatedly disciplined him, was found guilty Monday of masterminding a homemade bomb attack that disfigured and partially blinded the board's chairman.

A federal jury deliberated for a little over two days before convicting Dr. Randeep Mann, 52, of using a weapon of mass destruction and destroying a vehicle with an explosive in the February 2009 attack that nearly killed Dr. Trent Pierce.

Mann, a federal firearms dealer, also was convicted of illegally possessing 98 grenades and a machine gun. He was acquitted of illegally possessing a shotgun.

He faces up to life in prison for the weapon of mass destruction charge when he is sentenced on a later date.

Before the verdict was read, Mann smiled at his children and other family members who were watching from the courtroom gallery. He and his wife, Sangeeta "Sue" Mann, who was also on trial, spoke quietly to one another before hearing the jury's decision, as they had throughout the five-week-long trial.

One of Randeep Mann's sons began crying loudly when the first guilty verdict against his father was read. Other family members began crying as the drumbeat of guilty verdicts continued.

As jurors were filing out of the courtroom, Sue Mann collapsed into her chair, but she remained conscious. Her husband gently rubbed the back of her head with his hand.

Mann's family declined to comment after the verdict, as did Pierce's wife, Melissa, and their lawyer, Betsy Murray. Pierce was not in court Monday because he was seeing patients in his West Memphis medical clinic, and his attorney said he would not comment on the verdict.

U.S. District Judge Brian Miller allowed Sue Mann to remain free on bond pending her sentencing. Her husband was ordered to remain behind bars.

Prosecutors acknowledged having no forensic evidence connecting Mann to the bomb scene or proving he planted the explosive - made from a hand grenade duct-taped to a spare tire - in Pierce's driveway in West Memphis.

Defense attorneys argued investigators targeted the wrong person because of the family physician's race and his love of collecting weapons.

Defense attorney Blake Hendrix said he planned to appeal the verdict.

"We have an abiding conviction that the evidence in this case is legally insufficient to support this jury's verdict," Hendrix said.

Still, prosecutors argued, there were links, including an e-mail Mann sent to his brother in India with the subject line "Pierce" and a photograph of the doctor, with the text, "I hope this picture is good."

The bomb itself was made from a spare tire from a 2002 Nissan Altima, and prosecutors said a friend and business partner of Randeep Mann's had an Altima from which the spare was missing when federal agents executed a search warrant.

A friend of Randeep Mann's also testified that the doctor repeatedly said members of the Arkansas State Medical Board needed to suffer like he suffered.

"You don't have to have forensic evidence every time you try a case, and I think the jury understood that," assistant U.S. attorney Karen Whatley said.

Pierce, whose face remains speckled with bits of black tire still lodged in his skin from the bombing, led the panel that sanctioned Mann after complaints he was over-prescribing painkillers and other addictive drugs. The board revoked Mann's right to prescribe narcotics after complaints that 10 of his patients overdosed and died.

At the time of the bombing, the board was investigating whether Mann was continuing to prescribe controlled substances, despite the revocation of his Drug Enforcement Agency permit to do so.

Mann was convicted on seven of the eight charges he faced. Along with using a weapon of mass destruction, Mann was charged with destroying a vehicle with an explosive because the homemade bomb was placed next to Pierce's Lexus hybrid sport utility vehicle. The blast tore the bumper from the SUV.

Mann was initially arrested after 98 grenades were found buried in a clearing near his rural Pope County home. He was convicted of possessing those grenades, as well as an unregistered machine gun. The doctor had more than 100 firearms in gun safes in his home, but only two were found to be unregistered when federal agents executed a search warrant in March 2009.

Mann was acquitted of possessing an unregistered shotgun after jurors heard testimony that an official with the Bureau of Alcohol, Tobacco, Firearms and Explosives told Mann he didn't need to register the gun unless he sold it.

Mann and his wife also were convicted of obstruction of justice charges. She was acquitted of lying to a grand jury investigating the case.