A 22-year-old Fort Washington man was convicted of first-degree murder Wednesday in the May 2011 killings of two cousins who were shot during a robbery.

A Prince George’s County jury deliberated for about 21 / 2 hours before finding Brian Mayhew guilty in the deaths of Sean Ellis, 24, and Anthony McKelvin, 28. Police found the pair dead in a silver Lexus in Capitol Heights, their bodies soaked in bleach and the car covered in gasoline. Prosecutors say that Mayhew and an accomplice planned to light the car on fire to destroy evidence of their crimes but didn’t have a lighter.

The win for state prosecutors is particularly notable considering that their star witness, Nicoh Mayhew — who admitted that he was at the crime scene after the killings — was fatally shot in December 2012.

Authorities allege that from jail, Brian Mayhew ordered his uncle executed to keep him from testifying.

During the week-long trial, Christine Murphy and Jason Knight, Prince George’s assistant state’s attorneys, painted Brian Mayhew as a man willing to go to great lengths — even kill his uncle — to hide his crimes.

“As children, we’re taught to clean up after ourselves,” Murphy said. “Brian Mayhew takes that lesson to a whole new extreme.”

After Nicoh Mayhew’s death, a judge ruled that state prosecutors could read to jurors the statements he had made before a grand jury. In the testimony, he said his nephew asked him to bring bleach and gas to the crime scene. But Nicoh Mayhew felt as if he had been set up. So he cooperated with authorities, he said.

“I really didn’t have nothing to do with it,” Nicoh Mayhew said in his grand jury testimony. “Why am I going to lose my life on account of them?”

John M. McKenna, Mayhew’s attorney, argued that Nicoh Mayhew’s grand jury testimony could not be trusted because he had a motive to kill Ellis and McKelvin. He pinned the killings on Nicoh Mayhew and another man charged in the case, Kenan Myers.

Although they had all grown up together, called each other friends and started “hustling” together, Nicoh Mayhew, Ellis and McKelvin eventually became “competitors” in the drug trade and had drifted apart, McKenna said. The event that drove the biggest wedge between them was a drug deal that went bad weeks before Ellis and McKelvin were killed.

“We are here ultimately because Nicoh Mayhew and Kenan Myers lost $10,000 in a drug deal with Sean Ellis,” McKenna said. “They blamed him, and they killed him.”

Prosecutors played jurors telephone calls recorded from the county correctional facility that they said proved that Brian Mayhew instructed hitmen to kill his uncle.

If Brian Mayhew was blameless in Ellis’s and McKelvin’s deaths, why would he order his uncle dead, prosecutors asked. And why would Brian Mayhew laugh and say, “I may be getting out of here” after learning that his uncle was killed.

“The defendant realized his cleanup wasn’t done,” Murphy said of the alleged hit on Nicoh Mayhew’s life.

Mayhew faces life without parole and is scheduled to be sentenced in March. He will go to trial in September on separate murder charges in connection with his uncle’s death.

McKenna declined to comment on the verdict.

Prince George’s County State’s Attorney Angela Alsobrooks said the jury’s decision removes “a ruthless person” from the community.

“We have to send a message that retaliating against witnesses will not be tolerated, and it is not successful,” Alsobrooks said.

Myers, 27, whom authorities have accused as being Mayhew’s accomplice in the deaths of Ellis and McKelvin, is scheduled to go on trial in March.

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