ROCKVILLE, Md. (AP) – Washington-area sniper John Allen Muhammad was convicted of six more of the killings Tuesday after a trial in which he acted as his own attorney and the prosecution’s star witness was his young protege and partner in crime.

Muhammad, 45, is already under a death sentence in Virginia for a killing there. The most he can get for the six Maryland slayings is life in prison without parole.

The jury took slightly more than four hours to convict him after a four-week trial.

The trial marked the first time Lee Boyd Malvo testified against the man prosecutors say was his mentor and manipulator. During two days of testimony last week, Malvo, 21, gave the first inside account of the shootings and described Muhammad’s elaborate plans for a reign of terror.

According to Malvo, Muhammad planned two phases of attacks _ six shootings a day for a month, followed by a wave of bombings of school buses and children’s hospitals. Malvo said that when he asked Muhammad why, the older man replied: “For the sheer terror of it _ the worst thing you can do to people is aim at their children.”

Muhammad hoped to extort $10 million from authorities and use the money to set up a school in Canada to teach homeless children how to use guns and explosives, Malvo said.

Maryland prosecutors said they needed to put Muhammad on trial as insurance in case his conviction in Virginia was overturned. Some of the victims’ families had also sought a second trial, seeking an explanation for the random slayings that targeted people in parking lots and gas stations near the nation’s capital.

Ten people in all were killed, and three were wounded, in Virginia, Maryland and Washington, D.C., in the string of shootings that gripped the metropolitan area with fear.

Malvo’s testimony came after he agreed to plead guilty in the Maryland killings. He gave detailed descriptions of each shooting, even pointing out parking spaces where the sniper team’s car was parked.

Aside from Malvo’s testimony, Muhammad’s second trial followed much of the same blueprint as his first, with prosecutors telling jurors that Muhammad and Malvo roamed the area in a beat-up Chevrolet Caprice, firing .223-caliber bullets through a hole bored in its trunk.

The jury heard a torrent of evidence that linked Muhammad to the shootings _ fingerprints, DNA evidence, and ballistics tests that connected the bullets used in the shootings to the Bushmaster rifle found in the car when Muhammad and Malvo were arrested.

Acting as his own lawyer, Muhammad claimed he and Malvo were simply roaming the Washington region looking for his children who had been taken away from him in a custody battle with his ex-wife. He implied that authorities framed him, planting items such as DNA and gun evidence to convict him.

In an often testy four-hour cross-examination, Muhammad continued to refer to Malvo as his “son” even though the younger man tried to show during his testimony that he was no longer under the sway of his one-time father figure.

Malvo, who received no leniency in return for his testimony, told jurors he wanted to face the man who he said trained him to be a killer and coerced him to join his murderous schemes. Malvo called Muhammad a “coward” and said the older man had turned him into “a monster.”

Malvo told jurors that he shot three of the 13 sniper victims, while Muhammad pulled the trigger on the rest. He said Muhammad was the shooter in all but one of the six Maryland murders.

In March, Muhammad persuaded Circuit Judge James Ryan to let him defend himself, despite statements from two psychiatrists who said he may be mentally ill.

During closing arguments, Muhammad grew wild-eyed and sometimes shouted as he quoted the Bible, Mark Twain and Groucho Marx.

He struggled to mount a defense, hampered by his failure to meet deadlines on calling witnesses. He originally wanted to call hundreds of people to the stand, but the judge limited him to just a few dozen because he failed to follow proper courtroom procedure.

Many witnesses did not want to take part in his defense, refusing to show up at court even though they were issued subpoenas by lawyers helping Muhammad with his case.

In Maryland, Muhammad was charged with first-degree murder for the deaths in Montgomery County of James Martin, Premkumar Walekar, James “Sonny” Buchanan, Sarah Ramos, Lori Lewis Rivera and Conrad Johnson.

Maryland prosecutors originally sought a death sentence, but dropped those plans earlier this year. Muhammad’s Virginia defense attorneys and some victims questioned whether it was necessary to reopen old psychological wounds from more than three years ago.

Muhammad could still face prosecution for earlier shootings in Alabama and Louisiana. He and Malvo are linked to other shootings in Maryland, Arizona, Georgia and Washington state.