The man charged with killing a nun and maiming two others in a Prince William County car crash last year was found guilty Monday of felony murder.

Carlos A. Martinelly-Montano, 24, of Bristow slammed his car into another with three nuns inside about 8 a.m. on Aug. 1, 2010. The crash on Bristow Road in Bristow killed Sister Denise Mosier, 66, and seriously injured Sisters Connie Ruth Lupton and Charlotte Lange. All three belonged to the Benedictine Sisters of Virginia, who have a monastery in the town just west of Manassas.

Prince William Commonwealth’s Attorney Paul Ebert said after the trial that he was “pleased” with the verdict but “it’s a tragic case all around.”

Earlier Monday, Martinelly-Montano pleaded guilty to involuntary manslaughter, two counts of maiming while driving under the influence, driving on a revoked license and a third DWI offense within five years.

Martinelly-Montano is an illegal immigrant from Bolivia who became a lightning rod for advocates of stricter immigration enforcement after it was found that he had been arrested several times prior to the fatal crash.

The nun’s death outraged local and state officials and fueled a heated immigration debate. After the crash, Virginia stopped allowing work permit cards to be used as proof of legal residence, as Martinelly-Montano had done in order to work.

Because the crash resulted in Martinelly-Montano’s third DUI charge, it is considered a felony, Ebert said. In Virginia, felony murder means killing someone while committing a felony. The charge is usually applied to, for example, criminals who are robbing a store and kill an innocent bystander.

Ebert said in an interview Friday that he “used to consider the immigration status when I prosecuted people.”He no longer allows those charged with crimes to simply be deported by immigration officials, he said.

“Many times, they’re back in this country after a few months,” Ebert said. “I’ve often said these guys get back here quicker than I can with a passport.”

Sister Denise Mosier was killed in the car wreck and Sisters Connie Ruth Lipton and Charlotte Lange, both in their 70s, were badly injured in the crash.The nuns were part of the Benedictine Sisters, a well-known local organization that offers charitable services in Prince William County.

This post has been updated.