LOS ANGELES -- Former BART police Officer Johannes Mehserle emerged quietly from a Los Angeles jail early Monday after serving half of a two-year sentence for involuntary manslaughter in the shooting of unarmed train rider Oscar Grant.

The 12:01 a.m. release was "uneventful," said Steve Whitmore, a spokesman for the Los Angeles County sheriff. He declined to say exactly where Mehserle had gone after becoming a free man, but added, "We did make some special considerations for his safety."

Those considerations disappointed Grant's uncle, Cephus "Bobby" Johnson, who waited outside the main jail in Los Angeles. He said he wanted to see Mehserle leave and to force the former officer to see him.

Instead, Johnson and other relatives - who believe Mehserle should have been convicted of murder for the New Year's Day 2009 shooting - learned of the release through telephone and e-mail alerts sent before 12:30 a.m. by the National Victim Notification Network.

"If you have any concerns about your immediate safety," the alert stated, "contact your local law enforcement agency."

At about the same time, Mehserle's father, Todd Mehserle, sent a message to a Facebook page titled, "Free Johannes Mehserle," where supporters have shared their view that the 29-year-old former officer was unfairly vilified for making a mistake under pressure.

Mehserle supporters rejoice

The message read, "Johannes is free," prompting responses of "Welcome home," "Amen" and "Outstanding!!!!"

Mehserle's plans are unclear. His attorney, Michael Rains, has said the former officer looks forward to being with his girlfriend and son, who was born a day after the shooting.

Rains, who did not return calls seeking comment Monday, has also expressed concern about Mehserle's safety. The shooting prompted numerous protests, including a few that mushroomed into vandalism and looting in downtown Oakland.

Mehserle shot Grant, a 22-year-old Hayward resident, while trying to handcuff him on the platform of Fruitvale Station in Oakland. A second officer had pulled Grant from a Dublin-Pleasanton train after a fight before ordering him arrested for allegedly resisting.

On the witness stand, the former officer said he had meant to subdue Grant with a Taser shock weapon but had mistakenly fired his pistol into Grant's back.

Justice Department inquiry

Mehserle, now a parolee, is not in the clear. Xochitl Hinojosa, a spokeswoman for the U.S. Justice Department, said the agency's civil rights division was still reviewing the shooting to see if it warranted federal prosecution.

Also Monday, the National Lawyers Guild filed a class-action federal lawsuit saying Oakland police officers wrongfully arrested about 150 protesters after Mehserle's sentencing on Nov. 5. The suit says the arrestees, none of whom was charged, were then mistreated in Alameda County Jail, where some were held for nearly 24 hours.

Sheriff's Sgt. J.D. Nelson said protesters were held for longer than usual because there were so many to deal with and because some deputies were on riot patrol in Oakland. He disputed that the prisoners had been denied food and restrooms for long periods.