The former FBI agent convicted of motor vehicle manslaughter in connection with a 2011 drunken driving crash that killed one teenager and seriously injured another was sentenced Friday to 18 months in prison, authorities said.

Alhough state sentencing guidelines had called for a term of three months to four years, prosecutors had asked that Adrian Johnson, 39, be sentenced to ten years in prison for the February 2011 crash that killed 18-year-old Lawrence Garner Jr.

They had accused Johnson, 38, of speeding and driving drunk when he plowed into the side of a car as it pulled onto North Keys Road in February 2011. The crash killed Garner, who was driving, and seriously injured his best friend, Robert Mitchell II, as they returned home from a friend’s house after playing basketball.

At the time, Johnson was an FBI agent assigned to the U.S. attorney general’s protection detail. He was off duty when the crash occurred and resigned shortly after.

A jury convicted Johnson in October of motor vehicle manslaughter and six related charges.. He was jailed immediately after and will be given 71 days of credit for the time he has served, prosecutors said.

 Johnson’s defense attorney has said he will appeal the conviction. Prosecutors said Prince George’s County Circuit Court Judge Michael Pearson handed down the sentence.